Past records indicate that each of the 5 massive laser computer printers at the U.S. Department of Energy

(DOE), in Washington, DC, needs repair after about 20 hours of use. Breakdowns have been determined to be Poisson distributed. The one technician on duty can service a printer in an average of 2 hours, following an exponential distribution. Printer downtime costs $120 per hour. The technician is paid $25 per hour.

APPROACH c To compute the system’s operation characteristics we note that the mean arrival rate is l 5 1>20 5 0.05 printers/hour. The mean service rate is m 5 1>2 5 0.50 printers/hour.