There are two tennis courts. Pairs of players arrive at rate 3 per hour and play

for an exponentially distributed amount of time with mean one hour. If there are

already two pairs of players waiting new arrivals will leave. (a) Find the stationary

distribution for the number of courts occupied. (b) Find the rate at which customers

enter the system. (c) Find the expected amount of time a pair has to wait before they

can begin playing.