A customer would like a database design for an e-commerce website that sells books. He wants to store users, employees, inventory, and shopping cart data for each user. Once the user checks out, their cart data can be assumed to be cleared from the database. Only some employees can alter inventory data and the owner wants to be able to monitor who is making inventory changes for audits. How many relations would you need? What would they be? What attributes would each relation have? Which ones would be primary keys? What foreign keys would each relation have? What links do these create and why is it necessary? Given most databases can only store one item per attribute, how would the shopping cart be handled to allow for users to have an undetermined amount of items in their cart?