A customer can search for songs using the song title, artist's name, or album title. Search results are organized by albums and songs within each album. For each album, the site displays the artist name, the album title, a thumbnail image of the album cover, the year released, and the price of the album. For each song, the site displays the song title, the length of the song, and the price of the song. A customer can purchase an album or an individual song. The price of a purchased album or song is charged to the credit card on file for the customer, and the customer downloads the album or song. What classes can you identify from this description? What are some attributes of each class? What associations exist among the classes?