The problems for this chapter use a database for a simple department store that sells items to customers and wants to keep track of the invoices, the selling price (if an item is on sale), and the sales tax (7%) to be collected on some items. Every customer and invoice are assigned unique numbers. All items have a Universal Product Code (UPC) number and bar-code assigned to each unique item. Food and non-carbonated beverages are not taxed, but clothing, home goods, and most other items are.