Workers come to an internal supply store at the rate of one every 10 (+ or –) 4 minutes. Their requisitions are handled by one of three clerks; a clerk takes 22 (+ or -) 10 minutes to handle a requisition. All requisitions are then passed to a single cashier, who spends 7 (+ or -) 6 minutes per requisition. Simulate the system for 120 hours.