Customers arrive at a two-server system according to a Poisson process having rate λ = 5. An arrival ?nding server 1 free will begin service with that server. An arrival ?nding server 1 busy and server 2 free will enter service with server 2. An arrival ?nding both servers busy goes away. Once a customer is served by either server, he departs the system. The service times at server i are exponential with rates μi, where μ1 = 4, μ2 = 2.
(a) What is the average time an entering customer spends in the system?
(b) What proportion of time is server 2 busy?