Consider the 'last process' of manufacturing a car. The last two things that are done to a car before its manufacture is complete are installing the engine and putting on the tires. One worker is available to install the engine and can service an average of 60 cars per hour. After the engine is installed, the car goes to the tire station and waits for its tires to be attached. Three workers serve at the tire station. Each works on one car at a time and can put tires on a car in an average time of 3 minutes. The interarrival time car arrival in the 'last process' is 4 minutes. Both interarrival times and service times are exponential.

a) Determine the men queue length at each work station.

b) Determine the total expected time that a car spends waiting for service.