The Schmedley Discount Department Store has approximately 300customers shopping

The Schmedley Discount Department Store has approximately 300customers shopping in its store between 9 a.m. and 5 p.m. onSaturdays. In deciding how many cash registers to keep open eachSaturday Schmedleys manager considers two factors: customerwaiting time (and the associated waiting cost) and the servicecosts of employing additional checkout clerks. Checkout clerks arepaid an average of $8 per hour. When only one is on duty thewaiting time per customer is about 10 minutes (or 1/6 hour); whentwo clerks are on duty the average checkout time is 6 minutes perperson; 4 minutes when three clerks are working; and 3 minutes whenfour clerks are on duty.