diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..ed3c559c1 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,9 +1,11 @@
 // Predict and explain first...
-
+// I think, for object we have to use key as property value instead of array index in console.log.
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
 
+//Correct Code:
+
 const address = {
   houseNumber: 42,
   street: "Imaginary Road",
@@ -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..ecb3a1e0c 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,6 @@
 // Predict and explain first...
-
+// I think  we have to use the dot notation associated with the key with variable author to see the property values as output. 
+// Besides, we can omit for...of loop for this time cause there is no function for this program.
 // 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
 
@@ -11,6 +12,10 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
-  console.log(value);
-}
+  console.log(author.firstName);
+  console.log(author.lastName);
+  console.log(author.occupation);
+  console.log(author.age);
+  console.log(author.alive);
+
+
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..6ff683eb4 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,5 +1,6 @@
 // Predict and explain first...
-
+// My prediction is for log out the title, how many it serves and the ingridients we have to use several console.log for each of the property 
+// value. Besides, for each ingredient should be logged on a new line, we can use array index for the ingredients array.
 // 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?
@@ -10,6 +11,10 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
-console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+
+console.log(recipe.title);
+console.log(recipe.serves);
+console.log(recipe.ingredients[0]);
+console.log(recipe.ingredients[1]);
+console.log(recipe.ingredients[2]);
+console.log(recipe.ingredients[3]);
\ No newline at end of file
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..a07485828 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,6 @@
-function contains() {}
+function contains(input, propertyName) {
+  const result = Object.hasOwn(input, propertyName);
+  return result;
+}
 
 module.exports = contains;
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..4970c9227 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -1,35 +1,42 @@
 const contains = require("./contains.js");
 
-/*
-Implement a function called contains that checks an object contains a
-particular property
-
-E.g. contains({a: 1, b: 2}, 'a') // returns true
-as the object contains a key of 'a'
-
-E.g. contains({a: 1, b: 2}, 'c') // returns false
-as the object doesn't contains a key of 'c'
-*/
-
-// Acceptance criteria:
-
-// Given a contains function
-// When passed an object and a property name
-// Then it should return true if the object contains the property, false otherwise
-
-// Given an empty object
-// When passed to contains
-// Then it should return false
-test.todo("contains on empty object returns false");
-
-// Given an object with properties
-// When passed to contains with an existing property name
-// Then it should return true
-
-// Given an object with properties
-// When passed to contains with a non-existent property name
-// Then it should return false
-
-// Given invalid parameters like an array
-// When passed to contains
-// Then it should return false or throw an error
+test("contains on empty object returns false", function () {
+  const object = {};
+  const currentOutput = contains(object, "a");
+  const targetOutput = false;
+
+  expect(currentOutput).toBe(targetOutput);
+});
+
+test("contains with an existing property name should return true", function () {
+  const object = {
+    a: 1,
+    b: 2,
+    flower: "red",
+  };
+  const currentOutput = contains(object, "a");
+  const targetOutput = true;
+
+  expect(currentOutput).toBe(targetOutput);
+});
+
+test("contains with a non-existing property name should return false", function () {
+  const object = {
+    a: 1,
+    b: 2,
+    flower: "red",
+  };
+  const currentOutput = contains(object, "c");
+  const targetOutput = false;
+
+  expect(currentOutput).toBe(targetOutput);
+});
+
+test("contains with an array should return false", function () {
+  const object = ["a", "b", "c"];
+
+  const currentOutput = contains(object, "c");
+  const targetOutput = false;
+
+  expect(currentOutput).toBe(targetOutput);
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..2dfabaaa4 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,6 @@
-function createLookup() {
-  // implementation here
+function createLookup(countryCurrencyPairs) {
+  const keyValuePairs = Object.fromEntries(countryCurrencyPairs);
+  return keyValuePairs;
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..8bbff3ea9 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,35 +1,17 @@
 const createLookup = require("./lookup.js");
 
-test.todo("creates a country currency code lookup for multiple codes");
-
-/*
-
-Create a lookup object of key value pairs from an array of code pairs
-
-Acceptance Criteria:
-
-Given
- - An array of arrays representing country code and currency code pairs
-   e.g. [['US', 'USD'], ['CA', 'CAD']]
-
-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
- - The values are the corresponding currency codes
-
-Example
-Given: [['US', 'USD'], ['CA', 'CAD']]
-
-When
-createLookup(countryCurrencyPairs) is called
-
-Then
-It should return:
- {
-   'US': 'USD',
-   'CA': 'CAD'
- }
-*/
+test("creates a country currency code lookup for multiple codes", function () {
+  const arr = [
+    ["US", "USD"],
+    ["CA", "CAD"],
+    ["BD", "BDT"],
+  ];
+  const currentOutput = createLookup(arr);
+  const targetOutput = {
+    US: "USD",
+    CA: "CAD",
+    BD: "BDT",
+  };
+
+  expect(currentOutput).toEqual(targetOutput);
+});
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..e8f6b3297 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -4,10 +4,37 @@ function parseQueryString(queryString) {
     return queryParams;
   }
   const keyValuePairs = queryString.split("&");
+  const emptyElement = "";
 
-  for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
-    queryParams[key] = value;
+  for (i = 0; i < keyValuePairs.length; i++) {
+    const currentPair = keyValuePairs[i];
+    if (currentPair !== emptyElement) {
+      const index = currentPair.indexOf("=");
+      if (index !== -1) {
+        const key = currentPair.slice(0, index);
+        const value = currentPair.slice(index + 1);
+        const decodeKey = decodeURIComponent(key);
+        const decodeValue = decodeURIComponent(value);
+        const replacedKey = decodeKey.replace("+", " ");
+        const replacedValue = decodeValue.replace("+", " ");
+        if (queryParams.hasOwnProperty(replacedKey)) {
+          if (Array.isArray(queryParams[replacedKey])) {
+            queryParams[replacedKey].push(replacedValue);
+          } else {
+            queryParams[replacedKey] = [
+              queryParams[replacedKey],
+              replacedValue,
+            ];
+          }
+        } else {
+          queryParams[replacedKey] = replacedValue;
+        }
+      } else if (index === -1) {
+        const key = currentPair;
+        const value = "";
+        queryParams[key] = value;
+      }
+    }
   }
 
   return queryParams;
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 328b8df61..82bc37dfc 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -9,7 +9,7 @@ test("should parse values containing '='", () => {
   expect(parseQueryString("equation=a=b-2")).toEqual({
     equation: "a=b-2",
   });
-});
+}); 
 
 test("should ignore empty key-value pairs", () => {
   expect(parseQueryString("key1=value1&&key2=value2&")).toEqual({
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..cf1fc7460 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,21 @@
-function tally() {}
+function tally(array) {
+  if (array.length === 0) {
+    return {};
+  }
+  if (typeof array === "string") {
+    throw new Error();
+  }
+  const object = {};
+  for (i = 0; i < array.length; i++) {
+    const currentItem = array[i];
+    if (object.hasOwnProperty(currentItem)) {
+      object[currentItem] += 1;
+    } else {
+      object[currentItem] = 1;
+    }
+  }
+
+  return object;
+}
 
 module.exports = tally;
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..fe5558d39 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -1,34 +1,18 @@
 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 }
- */
+test("should return an empty object when given an empty array", () => {
+  expect(tally([])).toEqual({});
+});
 
-// Acceptance criteria:
+test("should return counts for each unique item when given an array with one item and with duplicate items", () => {
+  expect(tally(["a"])).toEqual({ a: 1 });
+  expect(tally(["a", "a", "a"])).toEqual({ a: 3 });
+  expect(tally(["a", "a", "b", "c"])).toEqual({ a: 2, b: 1, c: 1 });
+});
 
-// Given a function called tally
-// When passed an array of items
-// Then it should return an object containing the count for each unique item
-
-// 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");
-
-// Given an array with duplicate items
-// When passed to tally
-// Then it should return counts for each unique item
-
-// Given an invalid input like a string
-// When passed to tally
-// Then it should throw an error
+test("should throw an error when given an invalid input", () => {
+  function invalidInput() {
+    tally("string");
+  }
+  expect(invalidInput).toThrow(Error);
+});
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..b85480379 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -10,20 +10,33 @@ function invert(obj) {
   const invertedObj = {};
 
   for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
+    invertedObj[value] = key;
   }
 
   return invertedObj;
 }
 
+
+
 // 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}
+// { "1": "a", "2": "b"}
 
 // c) What does Object.entries return? Why is it needed in this program?
+// Object.entries() returns an array of an object's own enumerable string-keyed property [key, value] pairs. 
+// It is needed in this program because the invert function needs access to both the original keys and values 
+// so it can swap them and create a new inverted object.
 
 // d) Explain why the current return value is different from the target output
+// The current return value is different from the target output because invertedObj.key = value uses the word "key" as the property
+// name instead of using the actual key variable. It stores the values under the same property name "key", 
+// so it does not swap the original key and value. The correct code should use invertedObj[value] = key to create value:key pairs.
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+module.exports = invert;
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..4cf99ed0d
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,5 @@
+const invert = require("./invert.js");
+
+test("should return swaped keys and values for an given object", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ "1": "a", "2": "b"});
+});
\ No newline at end of file