Problem
1. Modify the simulation to have three runways, one always reserved for each of landing and takeoff and the third used for landings unless the landing queue is empty, in which case it can be used for takeoffs.
2. Modify the original (one-runway) simulation so that when each plane arrives to land, it will have (as one of its data members) a (randomly generated) fuel level, measured in units of time remaining. If the plane does not have enough fuel to wait in the queue, it is allowed to land immediately. Hence the planes in the landing queue may be kept waiting additional units, and so may run out of fuel themselves. Check this out as part of the landing function, and find about how busy the airport can become before planes start to crash from running out of fuel.
3. Write a stub to take the place of the random-number function. The stub can be used both to debug the program and to allow the user to control exactly the number of planes arriving for each queue at each time unit.