Two Sum

Write a function `multiply` that takes two integers `a` and `b` and returns their product. ## Function Signature ```function multiply(a, b);``` ### Example 1: > **Input:** `a = 3, b = 5`\ > **Output:** `15`\ > **Explanation:** The product of `3` and `5` is `15`. ### Example 2: > **Input:** `a = -2, b = -4`\ > **Output:** `8`\ > **Explanation:** The product of `-2` and `-4` is `8`. ### Example 3: > **Input:** `a = 0, b = 200`\ > **Output:** `0`\ > **Explanation:** The product of `0` and `200` is `0`.

Write a function `isEven` that takes an integer and returns true if it is even, false otherwise. ## Function Signature ```function isEven(num);``` ### Example 1: > **Input:** `num = 4`\ > **Output:** `true`\ > **Explanation:** The number 4 is even. ### Example 2: > **Input:** `num = 7`\ > **Output:** `false`\ > **Explanation:** The number 7 is not even. ### Example 3: > **Input:** `num = 0`\ > **Output:** `true`\ > **Explanation:** The number 0 is even.

Write a function `factorial` that takes a non-negative integer and returns its factorial. ## Function Signature ```function factorial(num);``` ### Example 1: > **Input:** `num = 5`\ > **Output:** `120`\ > **Explanation:** The factorial of 5 is `5! = 5 * 4 * 3 * 2 * 1 = 120`. ### Example 2: > **Input:** `num = 0`\ > **Output:** `1`\ > **Explanation:** The factorial of 0 is defined as `1`. ### Example 3: > **Input:** `num = 3`\ > **Output:** `6`\ > **Explanation:** The factorial of 3 is `3! = 3 * 2 * 1 = 6`.