Exercise One: In this exercise you will be creating two functions.
// Function One: Will be called 'multiply'.
// This function will take two parameters, both numbers
// This function will return the two numbers multiplied together.
// Function Two: Will be called 'calculator'.
// This function will take three parameters,
// First will be a callback function,
// Second and Third will be numbers.
// This function will return the two numbers passed into the callback function.
// NOTE: You can use the multiply function to test the calculator function, but understand that
// other callback functions will be passed into it as a test.