diff --git a/task-1/count-above-threshold.js b/task-1/count-above-threshold.js
index 7cf0418..69f3791 100644
--- a/task-1/count-above-threshold.js
+++ b/task-1/count-above-threshold.js
@@ -1 +1,9 @@
-//Your code here
+function countAboveThreshold(numbers, threshold) {
+  let count = 0;
+  for (let i = 0; i < numbers.length; i++) {
+    if (numbers[i] > threshold) count++;
+  }
+  return count;
+}
+
+console.log(countAboveThreshold([1, 2, 3, 20, 100], 9));
diff --git a/task-2/calculateAverage-test.js b/task-2/calculateAverage-test.js
new file mode 100644
index 0000000..9483c00
--- /dev/null
+++ b/task-2/calculateAverage-test.js
@@ -0,0 +1,58 @@
+import { test, expect } from "vitest";
+import { calculateAverage } from "./calculateAverage.js";
+
+test("returns the average of numbers in an array", () => {
+  const numbers = [2, 4, 6];
+
+  const result = calculateAverage(numbers);
+
+  expect(result).toBe(4);
+});
+
+test("returns the single element when array has one number", () => {
+  const numbers = [5];
+
+  const result = calculateAverage(numbers);
+
+  expect(result).toBe(5);
+});
+
+test("returns null for empty array", () => {
+  const numbers = [];
+
+  const result = calculateAverage(numbers);
+
+  expect(result).toBe(null);
+});
+
+test("returns null for non-array input", () => {
+  const numbers = "123";
+
+  const result = calculateAverage(numbers);
+
+  expect(result).toBe(null);
+});
+
+test("returns null when the array contains a non-number value", () => {
+  const numbers = [1, 2, "3"];
+
+  const result = calculateAverage(numbers);
+
+  expect(result).toBe(null);
+});
+
+test("returns the average for array with negative numbers", () => {
+  const numbers = [-2, -4, -6];
+
+  const result = calculateAverage(numbers);
+
+  expect(result).toBe(-4);
+});
+
+test("returns the average for array with floating point numbers", () => {
+  const numbers = [3.2, 1.2, 5.3];
+
+  const result = calculateAverage(numbers);
+
+  expect(result).toBe(3.233333333333333);
+});
diff --git a/task-2/calculateAverage.js b/task-2/calculateAverage.js
index 097ee0a..69f2811 100644
--- a/task-2/calculateAverage.js
+++ b/task-2/calculateAverage.js
@@ -1,20 +1,20 @@
-export function calculateAverage(numbers) {
-  if (!Array.isArray(numbers)) {
-    return null;
-  }
-
-  if (numbers.length === 0) {
-    return null;
-  }
-
-  let sum = 0;
-
-  for (const num of numbers) {
-    if (typeof num !== "number") {
-      return null;
-    }
-    sum += num;
-  }
-
-  return sum / numbers.length;
-}
+export function calculateAverage(numbers) {
+  if (!Array.isArray(numbers)) {
+    return null;
+  }
+
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  let sum = 0;
+
+  for (const num of numbers) {
+    if (typeof num !== "number") {
+      return null;
+    }
+    sum += num;
+  }
+
+  return sum / numbers.length;
+}
diff --git a/task-3/count-vowels-debug.js b/task-3/count-vowels-debug.js
index 1ce292b..01a85f8 100644
--- a/task-3/count-vowels-debug.js
+++ b/task-3/count-vowels-debug.js
@@ -1,17 +1,16 @@
 function countVowels(text) {
   let count = 0;
-
-  for (let i = 0; i <= text.length; i++) {
+  const lowerCase = text.toLowerCase();
+  for (let i = 0; i < lowerCase.length; i++) {
     if (
-      text[i] === "a" ||
-      text[i] === "e" ||
-      text[i] === "i" ||
-      text[i] === "o" ||
-      text[i] === "u"
+      lowerCase[i] === "a" ||
+      lowerCase[i] === "e" ||
+      lowerCase[i] === "i" ||
+      lowerCase[i] === "o" ||
+      lowerCase[i] === "u"
     ) {
       count++;
     }
   }
-
   return count;
 }
diff --git a/task-4/bigArray.js b/task-4/bigArray.js
index 070947a..982673b 100644
--- a/task-4/bigArray.js
+++ b/task-4/bigArray.js
@@ -1,12 +1,9 @@
-// you can use this function to generate a big array of the specified size
-// It contains numbers from 0 to size - 1
-// Example: generateBigArray(5) will return [0, 1, 2, 3, 4]
 function generateBigArray(size) {
   const array = new Array(size);
   for (let i = 0; i < size; i++) {
     array[i] = i;
   }
   return array;
-};
+}
 
-export default generateBigArray;
\ No newline at end of file
+export default generateBigArray;
diff --git a/task-4/search-experiment.js b/task-4/search-experiment.js
index 63c189a..0787138 100644
--- a/task-4/search-experiment.js
+++ b/task-4/search-experiment.js
@@ -1,3 +1,60 @@
-// Write your code here
-// Use generateBigArray to create a big array numbers.
-// Example: generateBigArray(1000000) will create an array of 1 million numbers.
\ No newline at end of file
+import generateBigArray from "./bigArray.js";
+
+function getTargetByBinarySearch(array, target) {
+  let left = 0,
+    right = array.length - 1;
+  while (left <= right) {
+    const middle = left + Math.floor((right - left) / 2);
+    if (array[middle] < target) {
+      left = middle + 1;
+    } else if (array[middle] > target) {
+      right = middle - 1;
+    } else {
+      return middle;
+    }
+  }
+  return false;
+}
+
+function getTargetByLinearSearch(array, target) {
+  for (let i = 0; i < array.length; i++) {
+    if (array[i] === target) {
+      return i;
+    }
+  }
+  return false;
+}
+
+console.time("Linear Search 1k");
+getTargetByLinearSearch(generateBigArray(1000), 10540640);
+console.timeEnd("Linear Search 1k");
+
+console.time("Linear Search 100k");
+getTargetByLinearSearch(generateBigArray(100000), 10540640);
+console.timeEnd("Linear Search 100k");
+
+console.time("Linear Search 1M");
+getTargetByLinearSearch(generateBigArray(10000000), 10540640);
+console.timeEnd("Linear Search 1M");
+
+console.time("Linear Search 10M");
+getTargetByLinearSearch(generateBigArray(10000000), 10540640);
+console.timeEnd("Linear Search 10M");
+
+console.log("---");
+
+console.time("Binary Search 1k");
+getTargetByBinarySearch(getTargetByBinarySearch(1000), 10540640);
+console.timeEnd("Binary Search 1k");
+
+console.time("Binary Search 100k");
+getTargetByBinarySearch(generateBigArray(100000), 10540640);
+console.timeEnd("Binary Search 100k");
+
+console.time("Binary Search 1M");
+getTargetByBinarySearch(generateBigArray(10000000), 10540640);
+console.timeEnd("Binary Search 1M");
+
+console.time("Binary Search 10M");
+getTargetByBinarySearch(generateBigArray(10000000), 10540640);
+console.timeEnd("Binary Search 10M");