$5\mathrm{.}21.$ The following problem was once used on an exam:

Jurassic Park consists of a dinosaur museum and a park for safari riding. There are $m$ passengers and $n$ single$-$passenger cars. Passengers wander around the museum for a while, then line up to take a ride in a safari car. When a car is available, it loads the one passenger it

can hold and rides around the park for a random amount of time. If the $n$ cars are all out riding passengers around, then a passenger who wants to ride waits; if a car is ready to load but the are no waiting passengers, then the car waits. Use semaphores to synchronize the $m$ passenger processes and the $n$ car processes.