An automated car wash serves customers with the following serial process: pretreat, wash, rinse, wax, hand dry. Each of these steps is performed by a dedicated machine except for the hand-dry step, which is performed manually on each car by one of three workers. The steps of the process have the following processing times:

• Pretreat: 3 minute per car
• Wash: 5 minutes per car
• Rinse: 2 minutes per car
• Wax: 2 minutes per car
• Hand dry: 7 minutes per car

F. Now assume demand is 15 cars per hour. Starting from an empty system (and assuming the stations can work independently), how long would it take (minutes) to wash 8 cars?