this scoping. Your task is to create four arrow functions with specific functionality.
- Create an 'add' function that takes two parameters and returns their sum.
- Create a 'multiply' function that takes two parameters and returns their product.
- Create an 'isEven' function that evaluates if a number is even or not.
- Create a 'square' function that computes the square of a single parameter.
Be sure to export your arrow functions to be evaluated correctly.