In an airplane, each passenger has a touch screen for ordering a drink and a snack. Some items are free and some are not. The system prepares two reports for speeding up service:

1. A list of all seats, ordered by row, showing the charges that must be collected.
2. A list of how many drinks and snacks of each type must be prepared for the front and the rear of the plane.

Follow the design process that was described in this chapter to identify classes, and implement a program that simulates the system.