Sal (see Problem 9-18) is considering changing the queuing characteristics of his shop. Instead of selecting a number for the first available barber, a customer will be able to select which barber he or she prefers upon arrival. Assuming that this selection does not change while the customer is waiting for his or her barber to become available and that the requests for each of the four barbers are evenly distributed, answer the following:
(a) What is the average number of customers in the barber shop?
(b) What is the average time spent in the shop?
(c) What is the average time a customer spends waiting to be called to a chair?
(d) What is the average number of customers waiting to be served?
(e) Explain why the results from Problems 9-18 and 9-19 differ.