Two Trouble-Shooters Handle Service Calls for 10 Machines

Essay

Two trouble-shooters handle service calls for 10 machines.The average time between service requirements is 18 days,and service time averages 2 days.Assume exponential distributions.While running,each machine can produce 1,500 pieces per day.Determine:
(i)the percentage of time trouble-shooters are idle
(ii)each machine's net productivity
(iii)If trouble-shooters represent a cost of $150 per day,and machine downtime cost is $600 per day,would another trouble-shooter be justified?
Explain.