Benny's arcade has four video game machines. The average time between machine failures is 50 hours. Jimmy, the maintenance manager can repair a machine in 5 hours on average. The machines have an exponential failure distribution, and Jimmy has an exponential service-time distribution.
a. Jimmy's utilization is?
b. what is the average number of machines out of service, that is, waiting to be repaired or being repaired?
c. what is the average time a machine is out of service?