Explain briefly the queuing theory. Customers arrive at a one-man barber shop according to Poisson process with mean inter arrival time of 12 minutes. Customer spends an average of 10 minutes in the barber’s chair. What is the expected number of customers in the barber shop in the queue?

Queuing theory is the mathematical study of waiting lines. It models systems in which customers (or jobs) arrive, possibly wait in a queue, receive service from one or more servers, and then leave. Its aim is to predict system performance measures such as average waiting time, queue length, and s...