Problem Statement

A software subsystem of an air-traffic control system is defined to manage a queue of aircraft (AC) in an airport. The aircraft queue is managed by a process that responds to three types of requests:

1. System boot used to start the system.
2. Enqueue aircraft used to insert a new AC into the system.
3. Dequeue aircraft used to remove an AC from the system.

AC’s have at least (but are not limited to having) the following properties:

1. AC type: Passenger or Cargo
2. AC size: Small or Large

The process that manages the queue of AC’s satisfies the following:

1. There is no limit to the number of AC’s it can manage.
2. Dequeue aircraft requests result in selection of one AC for removal such that: a. Passenger AC’s have removal precedence over Cargo AC’s. b. Large AC’s of a given type have removal precedence over Small AC’s of the same type. c. Earlier enqueued AC’s of a given type and size have precedence over later enqueued AC’s of the same type and size.