12. Musixscore.com is an online service providing sheet music to customers. On the browse music web page, customers select a genre of music from a drop-down list. The web page uses Ajax to obtain a list of performers, musicians, or groups that match the genre, which is formatted as a drop-down list. When a selection is made from the performers drop-down list, the web page uses Ajax to display a third drop-down list displaying all the CDs or other works of the performer. When a CD is selected, the web page uses Ajax to obtain all the songs on the CD in a fourth drop-down list. The viewer may make multiple selections. When the Add to Shopping Cart image is clicked, the songs are added to the shopping cart. The viewer may change any of the drop-down lists to select additional sheet music, and the process is repeated. a. Write a use case description for the Browse Music Score use case, representing this activity.

Create a class diagram for the entity classes used in the sequence diagram.