diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..b0b0fa890 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,4 +1,6 @@
 // Predict and explain first...
+//Its will say undefined. This is because the address object does not have an index of 0.
+// To access the houseNumber property of the address object, we need to use dot notation or bracket notation with the property name as a string
 
 // This code should log out the houseNumber from the address object
 // but it isn't working...
@@ -12,4 +14,4 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address.houseNumber}`);
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..150c86742 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,7 +1,8 @@
 // Predict and explain first...
-
+// It will throw a TypeError.Because a for of loop only can go throuhgh things like strings and arrays but not object.
 // This program attempts to log out all the property values in the object.
 // But it isn't working. Explain why first and then fix the problem
+// To print the value of the object , we use object.values() because it turn the object into list of value that er can loop through and log.
 
 const author = {
   firstName: "Zadie",
@@ -11,6 +12,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..60c52a355 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,9 +1,10 @@
 // Predict and explain first...
-
+// It will trown an error. However my perdiction was wrong it  doesn't throw errow ,instead it print the ingredients array and [ object object] 
+// because of the whole recipe object is being converted to string.
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
 // How can you fix it?
-
+// I fixed by used the join () method to print the each ingredient on new line.
 const recipe = {
   title: "bruschetta",
   serves: 2,
@@ -12,4 +13,4 @@ const recipe = {
 
 console.log(`${recipe.title} serves ${recipe.serves}
   ingredients:
-${recipe}`);
+${recipe.ingredients.join('\n  ')}`);
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..c18b20de8 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,9 @@
-function contains() {}
+function contains(obj, prop) {
+  if (typeof obj !== "object" || obj === null || Array.isArray(obj)) {
+    return false;
+  }
+
+  return Object.prototype.hasOwnProperty.call(obj, prop);
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..c12d86abb 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,16 +20,26 @@ as the object doesn't contains a key of 'c'
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
+test("contains on empty object returns false", () => {
+  expect(contains({}, "a")).toBe(false);
+});
 
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
+test("returns true when property exists", () => {
+  expect(contains({ a: 1, b: 2 }, "a")).toBe(true);
+});
 
 // Given an object with properties
 // When passed to contains with a non-existent property name
 // Then it should return false
-
+test("return false when property does not exit", () => {
+  expect(contains({ a: 1, b: 2 }, "c")).to(fasle);
+});
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+test("return false for invalid input like an array", () => {
+  expect(contains([], "a")).toBe(false);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..0982efe9c 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,14 @@
-function createLookup() {
-  // implementation here
+function createLookup(pairs) {
+  if (!Array.isArray(pairs)) return {};
+  const lookup = {};
+
+  for (const pair of pairs) {
+    if (!Array.isArray(pair) || pair.length !== 2) continue;
+
+    const [country, currency] = pair;
+    lookup[country] = currency;
+  }
+  return lookup;
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..11ab7dfa2 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,33 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
+test("creates a country currency code lookup for multiple codes", () => {
+  const input = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+  ];
+
+  const result = createLookup(input);
+
+  expect(result).toEqual({
+    US: "USD",
+    CA: "CAD",
+  });
+});
+test("returns an empty object for an empty array", () => {
+  expect(createLookup([])).toEqual({});
+});
+
+test("returns an empty object for invalid input", () => {
+  expect(createLookup("not-an-array")).toEqual({});
+});
+
+test("ignores invalid pairs inside array", () => {
+  const input = [["US", "USD"], ["CA"], "invalid"];
+
+  expect(createLookup(input)).toEqual({
+    US: "USD",
+  });
+});
 
 /*
 
@@ -15,6 +42,7 @@ Given
 When
  - createLookup function is called with the country-currency array as an argument
 
+
 Then
  - It should return an object where:
  - The keys are the country codes
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..65ab80416 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -1,12 +1,20 @@
 function parseQueryString(queryString) {
-  const queryParams = {};
-  if (queryString.length === 0) {
-    return queryParams;
+  if (typeof queryString !== "string" || queryString.length === 0) {
+    return {};
   }
+
+  const queryParams = {};
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    if (!pair) continue;
+
+    const index = pair.indexOf("=");
+    if (index === -1) continue;
+
+    const key = pair.slice(0, index);
+    const value = pair.slice(index + 1);
+
     queryParams[key] = value;
   }
 
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..daf391ddc 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -3,10 +3,32 @@
 // Below is one test case for an edge case the implementation doesn't handle well.
 // Fix the implementation for this test, and try to think of as many other edge cases as possible - write tests and fix those too.
 
-const parseQueryString = require("./querystring.js")
+const parseQueryString = require("./querystring.js");
 
 test("parses querystring values containing =", () => {
   expect(parseQueryString("equation=x=y+1")).toEqual({
-    "equation": "x=y+1",
+    equation: "x=y+1",
+  });
+});
+
+test("returns empty object for empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("returns empty object for empty string", () => {
+  expect(parseQueryString("")).toEqual({});
+});
+
+test("parses multiple key value pairs", () => {
+  expect(parseQueryString("a=1&b=2")).toEqual({
+    a: "1",
+    b: "2",
+  });
+});
+
+test("ignores invalid pairs without =", () => {
+  expect(parseQueryString("a=1&invalid&b=2")).toEqual({
+    a: "1",
+    b: "2",
   });
 });
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..0bdcdb4e5 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,15 @@
-function tally() {}
+function tally(items) {
+  if (!Array.isArray(items)) {
+    throw new Error("Expected an array");
+  }
+
+  const counts = {};
+
+  for (const item of items) {
+    counts[item] = (counts[item] || 0) + 1;
+  }
+
+  return counts;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..7c06c7978 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -19,16 +19,69 @@ const tally = require("./tally.js");
 // Given a function called tally
 // When passed an array of items
 // Then it should return an object containing the count for each unique item
+test("tally on an array with duplicate items returns correct counts", () => {
+    expect(tally(['a', 'a', 'b', 'c'])).toEqual({ a: 2, b: 1, c: 1 });
+});
 
 // Given an empty array
 // When passed to tally
 // Then it should return an empty object
-test.todo("tally on an empty array returns an empty object");
+test("tally on an empty array returns an empty object", () => {
+    expect(tally([])).toEqual({});
+});
 
 // Given an array with duplicate items
 // When passed to tally
 // Then it should return counts for each unique item
+const tally = require("./tally.js");
+
+/**
+ * tally array
+ *
+ * In this task, you'll need to implement a function called tally
+ * that will take a list of items and count the frequency of each item
+ * in an array
+ *
+ * For example:
+ *
+ * tally(['a']), target output: { a: 1 }
+ * tally(['a', 'a', 'a']), target output: { a: 3 }
+ * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
+ */
+
+// Acceptance criteria:
+
+// Given a function called tally
+// When passed an array of items
+// Then it should return an object containing the count for each unique item
+test("tally on an array with duplicate items returns correct counts", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+});
+
+// Given an empty array
+// When passed to tally
+// Then it should return an empty object
+test("tally on an empty array returns an empty object", () => {
+  expect(tally([])).toEqual({});
+});
+
+// Given an array with duplicate items
+// When passed to tally
+// Then it should return counts for each unique item
+test("tally countss for each unique item", () => {
+  expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+});
+
+// Given an invalid input like a string
+// When passed to tally
+// Then it should throw an error
+test(" tally throws an error for invalid input", () => {
+  expect(() => tally("not-an-array")).toThrow();
+});
 
 // Given an invalid input like a string
 // When passed to tally
 // Then it should throw an error
+test(" tally throws an error for invalid input", () => {
+  expect(() => tally("not-an-array")).toThrow();
+});
\ No newline at end of file
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..47ded0753 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -17,13 +17,42 @@ function invert(obj) {
 }
 
 // a) What is the current return value when invert is called with { a : 1 }
+{
+  key: 1;
+}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
-
+{
+  key: 2;
+}
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+return { 1: "a", 2: "b" };
 
 // c) What does Object.entries return? Why is it needed in this program?
+// Object.entries returns an array of key-value pairs from an object.
+//It is needed so we can loop through the object and access both keys and values.
+Object.entries({ a: 1, b: 2 });
+// [["a", 1], ["b", 2]]
 
 // d) Explain why the current return value is different from the target output
-
+//The current output is wrong because invertedObj.key uses a fixed property name instead of the variable key, so it overwrites the same property each time.
+//It should use invertedObj[value] = key to properly swap keys and values.
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+const invert = require("./invert.js");
+
+test("inverts a normal object", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({
+    1: "a",
+    2: "b",
+  });
+});
+
+test("inverts a single pair", () => {
+  expect(invert({ x: 10 })).toEqual({
+    10: "x",
+  });
+});
+
+test("returns empty object when input is empty", () => {
+  expect(invert({})).toEqual({});
+});
diff --git a/Sprint-2/stretch/count-words.js b/Sprint-2/stretch/count-words.js
index 8e85d19d7..e1cfbbfc4 100644
--- a/Sprint-2/stretch/count-words.js
+++ b/Sprint-2/stretch/count-words.js
@@ -1,28 +1,24 @@
-/*
-  Count the number of times a word appears in a given string.
-
-  Write a function called countWords that
-    - takes a string as an argument
-    - returns an object where
-          - the keys are the words from the string and
-          - the values are the number of times the word appears in the string
-
-  Example
-  If we call countWords like this:
-
-  countWords("you and me and you") then the target output is { you: 2, and: 2, me: 1 }
-
-  To complete this exercise you should understand
-    - Strings and string manipulation
-    - Loops
-    - Comparison inside if statements
-    - Setting values on an object
-
-## Advanced challenges
-
-1. Remove all of the punctuation (e.g. ".", ",", "!", "?") to tidy up the results
-
-2. Ignore the case of the words to find more unique words. e.g. (A === a, Hello === hello)
-
-3. Order the results to find out which word is the most common in the input
-*/
+function countWords(str) {
+  // handle empty or invalid input
+  if (typeof str !== "string") {
+    throw new Error("Expected a string");
+  }
+
+  // 1. clean string (remove punctuation + lowercase)
+  const cleanStr = str.replace(/[.,!?]/g, "").toLowerCase();
+
+  // 2. split into words
+  const words = cleanStr.split(" ");
+
+  // 3. count words
+  const result = {};
+  for (const word of words) {
+    if (word !== "") {
+      result[word] = (result[word] || 0) + 1;
+    }
+  }
+
+  return result;
+}
+
+module.exports = countWords;
diff --git a/Sprint-2/stretch/mode.js b/Sprint-2/stretch/mode.js
index 3f7609d79..e28c49984 100644
--- a/Sprint-2/stretch/mode.js
+++ b/Sprint-2/stretch/mode.js
@@ -8,29 +8,40 @@
 // refactor calculateMode by splitting up the code
 // into smaller functions using the stages above
 
-function calculateMode(list) {
-  // track frequency of each value
+function getFrequencies(list) {
   let freqs = new Map();
 
   for (let num of list) {
-    if (typeof num !== "number") {
-      continue;
-    }
+    if (typeof num !== "number") continue;
 
     freqs.set(num, (freqs.get(num) || 0) + 1);
   }
 
-  // Find the value with the highest frequency
+  return freqs;
+}
+
+function findMode(freqs) {
   let maxFreq = 0;
   let mode;
+
   for (let [num, freq] of freqs) {
     if (freq > maxFreq) {
-      mode = num;
       maxFreq = freq;
+      mode = num;
     }
   }
 
   return maxFreq === 0 ? NaN : mode;
 }
 
+function calculateMode(list) {
+  const freqs = getFrequencies(list);
+  return findMode(freqs);
+}
+
 module.exports = calculateMode;
+
+// Explanation:
+getFrequencies(list) //counts how many times each number appears
+findMode(freqs) // finds the number with the highest frequency
+calculateMode(list) // combines both steps
\ No newline at end of file
diff --git a/Sprint-2/stretch/mode.test.js b/Sprint-2/stretch/mode.test.js
index ca33c28a3..a9576c450 100644
--- a/Sprint-2/stretch/mode.test.js
+++ b/Sprint-2/stretch/mode.test.js
@@ -5,28 +5,43 @@ const calculateMode = require("./mode.js");
 // Given an array of numbers
 // When calculateMode is called on the array
 // Then it should return the number that appears most frequently in the array
-
-// Example:
-// Given [2,4,1,2,3,2,1]
-// When calculateMode is called on [2,4,1,2,3,2,1]
-// Then it should return 2 */
-
+// Answer:
 describe("calculateMode()", () => {
   test("returns the most frequent number in an array", () => {
     const nums = [2, 4, 1, 2, 3, 2, 1];
-
     expect(calculateMode(nums)).toEqual(2);
   });
 
-  test("returns the first mode in case of multiple modes", () => {
-    const nums = [1, 2, 2, 3, 3];
+  // Example:
+  // Given [2,4,1,2,3,2,1]
+  // When calculateMode is called on [2,4,1,2,3,2,1]
+  // Then it should return 2
+  // Answer:
+  test("returns 2 as the most frequent number", () => {
+    expect(calculateMode([2, 4, 1, 2, 3, 2, 1])).toEqual(2);
+  });
 
-    expect(calculateMode(nums)).toEqual(2);
+  // Given an array with multiple modes
+  // When calculateMode is called
+  // Then it should return the first mode
+  // Answer:
+  test("returns first mode when there is a tie", () => {
+    expect(calculateMode([1, 2, 2, 3, 3])).toEqual(2);
   });
 
+  // Given an array with non-number values
+  // When calculateMode is called
+  // Then it should ignore non-number values
+  // Answer:
   test("ignores non-number values", () => {
-    const nums = [1, 3, "2", 2, 3, null];
+    expect(calculateMode([1, 3, "2", 2, 3, null])).toEqual(3);
+  });
 
-    expect(calculateMode(nums)).toEqual(3);
+  // Given an empty array
+  // When calculateMode is called
+  // Then it should return NaN
+  // Answer:
+  test("returns NaN for empty array", () => {
+    expect(calculateMode([])).toBeNaN();
   });
 });
diff --git a/Sprint-2/stretch/till.js b/Sprint-2/stretch/till.js
index 6a08532e7..9ec49c7c1 100644
--- a/Sprint-2/stretch/till.js
+++ b/Sprint-2/stretch/till.js
@@ -23,9 +23,38 @@ const till = {
 const totalAmount = totalTill(till);
 
 // a) What is the target output when totalTill is called with the till object
+("£4.40");
 
 // b) Why do we need to use Object.entries inside the for...of loop in this function?
+// We use Object.entries() to convert the object into key-value pairs so we can loop through each coin type and its quantity using a for...of loop.
 
 // c) What does coin * quantity evaluate to inside the for...of loop?
+//It calculates the total value in pence for each coin type.
+
+//"1p" * 10 = 10
+//"50p" * 4 = 200
+
+// So it gives the total pence for each coin type.
 
 // d) Write a test for this function to check it works and then fix the implementation of totalTill
+Eg: test("calculates total till value correctly", () => {
+  const till = {
+    "1p": 10,
+    "5p": 6,
+    "50p": 4,
+    "20p": 10,
+  };
+
+  expect(totalTill(till)).toEqual("£4.40");
+});
+//then fix the implementation of totalTill
+function totalTill(till) {
+  let total = 0;
+
+  for (const [coin, quantity] of Object.entries(till)) {
+    const value = parseInt(coin);
+    total += value * quantity;
+  }
+
+  return `£${(total / 100).toFixed(2)}`;
+}