Acustomer owns several shopping carts. a shopping cart is identified by a shopping_cart_id and contains several books. some shopping carts may contain more than one copy of same book. the database records the number of copies of each book in any shopping cart. at that time, more information will be needed to complete the transaction. usually, the customer will be asked to fill or select a billing address, a shipping address, a shipping option, and payment information such as credit card number. an email notification is sent to the customer as soon as the order is placed