Consider the E-R diagram in Figure 7.29, which models an online bookstore.

a. List the entity sets and their primary keys.

b. Suppose the bookstore adds Blu-ray discs and downloadable video to its collection. The same item may be present in one or both formats, with differing prices. Extend the E-R diagram to model this addition, ignoring the effect on shopping baskets.

c. Now extend the E-R diagram, using generalization, to model the case where a shopping basket may contain any combination of books, Blu-ray discs, or downloadable video.

Reference Figure 7.29:

Database Design and the E-R Model.

author name address URL written by book ISBN title year price number contains number stocks publisher name address phone URL published by shopping_basket basket_id warehouse code address phone Figure 7.29 E-R diagram customer email name address phone basket_of