Make a track class that has a name, list of artists, duration, and price
reduce the price of a track by the discount amount
reset the track's price back to it's original price
Edits the set_discount so that discounts do not stack
create a new album with a name and a list of tracks
Albums have a duration
calculate the total price of an album
Albums have artits that you can look at alphabetical array unique.
check if an album is a single
raise an error if an album is created without any tracks