Question: A milling-machine department has 10 machines. The runtime until failure occurs on a machine is exponentially distributed with a mean of 20 hours. Repair times are uniformly distributed between 3 and 7 hours. Select an appropriate run length and appropriate initial conditions.
(a) How many repair persons are needed to ensure that the mean number of machines running is greater than eight?
(b) If there are two repair persons, estimate the number of machines that are either running or being served.