Problem
1. Write a function mirror Back To Front that mirrors the second half of a sound onto the first half.
2. Write a function mirror Front To Back that mirrors the first half of a sound onto the second half.
3. Write a function called reverse K that takes a sound and an integer k as input, and reverses the sound in intervals of size k seconds and returns the result. That is, in the returned sound, the first k seconds of the original sound play in reverse, then the next k seconds and so on.