Given the following problem description, draw a UML class diagram: A vending machine sells small, packaged, ready to eat items (chocolate bars, cookies, candies, etc.). Each item has a price and a name. A customer can buy an item, using a smart card (issued by the vending machine company) to pay for it. No other payment forms (i.e. cash, credit card) are allowed. The smart card records on it the amount of money available. The functions supported by the system are: a. Sell an item (choose from a list of items, pay item, distribute item) b. Recharge the machine c. Set up the machine (define items sold and price of items) d. Monitor the machine (number of items sold, number of items sold per type, total revenue) The system can be used by a customer, a maintenance employee (who recharges items in the machines), an administrator (who sets up the machine).