4. [25 points] A tool crib has exponential interarrival and service times and serves a very large group of mechanics. The mean time between arrivals is 4 minutes. It takes 3 minutes on the average for a tool-crib attendant to service a mechanic. The attendant is paid $10 per hour and the mechanic is paid $15 per hour. Assuming that mechanics impose costs on the system while in the queue and in service, would it be advisable to have a second tool-crib attendant? (Hint: You are now considering two queueing systems, i.e., MM 1 and MM2.)