ABS Specializes in Repair and Maintenance of Industrial Machines

Multiple Choice

ABS specializes in repair and maintenance of industrial machines.One repair technician has been assigned to five identical grinding machines for repair and maintenance.The machine breaks down after about 20 hours of use,and breakdowns have a Poisson probability distribution.It takes 6 hours to repair a machine,and repair times follow an exponential distribution.Machine downtime costs the company $250 an hour,and the technician is paid $50 an hour.Determine the average number of machines working.

A) 3.59
B) 2.87
C) 3.43
D) 2.54