For this program, you should prompt the user for an automobile service and how much they paid, and then calculate how much change the user should receive. So if you imagine standing at the counter, you ask them what service they would like, and then you collect their payment. You would then check how much they paid against the cost of the service they requested. If they did not pay enough, you would tell that to the customer. If a service is requested that is not provided, this would also be said to the customer. If the service is offered and the customer paid enough, then you would let them know how much change they will receive for that service.