M6_IND4. A chemical plant stores spare parts for maintenance in a large warehouse. Throughout the working day, maintenance personnel go to the warehouse to pick up supplies needed for their jobs. The warehouse receives a request for supplies, on average, every three minutes. The average request requires 2.6 minutes to fill. Maintenance employees are paid $24 per hour and warehouse employees are paid $14 per hour. The warehouse operates 8 hours per day.