Trucks arrive at the loading dock of a wholesale grocer at the rate of 1.2 per hour. A single crew consisting of two workers can load a truck in about 30 minutes. Crew members receive $ 10 per hour in wages and fringe benefits, and trucks and drivers reflect an hourly cost of $ 60. The man-ager is thinking of adding another member to the crew. The service rate would then be 2.4 trucks per hour. Assume rates are Poisson.
a. Would the third crew member be economical?
b. Would a fourth member be justifiable if the resulting service capacity were 2.6 trucks per hour?