Lemon Scooters assembly process is a simple line flow with three steps: deck assembly, wheel assembly, and packaging. Two types of scooters are made in this line, the Lemon-Ultra and the Lemon-Street. The market demand for Lemon-Ultra is the same as the market demand for Lemon-Street. In the Deck Assembly step, processing time is 0.5 minute per unit for both types of scooters. Currently the production batch size at the Desk Assembly is 50 units for Lemon-Ultra and 100 units for Lemon-Street. The set-up time for each batch of Lemon-Ultra is 10 minutes and 30 minutes for Lemon-Street. In the Wheel Assembly step, processing time is 1 minute per unit for both types of scooters. Currently the production batch size at the Wheel Assembly is 100 units for both types of scooters. The wheel assembly tool needs to be replaced before processing each batch. The replacement time is 20 minutes for both types of scooters (this is the set-up time for each batch). The Packaging step processes scooters unit by unit (there is no batching in the Packaging step). It takes 0.5 minute per unit for both types. (There is no difference to package either type of scooters.) The plant operates 24 hours a day, 7 days a week.

(8 points) Suppose all three steps process at the bottleneck rate that you calculated (in other words, the non-bottleneck steps slow down and process at the rate of the bottleneck). Assuming that at time t=0, there is a finished batch from Wheel Assembly and just arrived the Packaging station. Thus, the WIP buffer in front of Packaging station starts a maximum level of 100 units at t=0 and decreases at the bottleneck rate. What is the average time in hour that a scooter is spent in the WIP buffer?