Use Semaphores to simulate operation of one-product vending machine. Keep track of number of products keeping in machine and amount of money customer has inserted. Two processes are utilized, one which accepts money and keeps track of amount paid, and another which delivers product and change when adequate amount of money and machine's product button has been pushed. When inadequate amount of money has been entered, or when no products keep in machine, machine must return no product and it must return full amount deposited.