Yum and Yee food truck operates on Yale campus and serves customers during lunchtime every weekday. The food truck's specialty is seafood and its limited menu consists of two choices for the customers: seafood stir-fry and lobster roll. Customers arrive at the food truck at a constant rate during lunchtime. Assume that there is no variability in the customer arrival process. Each customer places exactly one lunch order: 60% of the customers order stir-fry and 40% of them order lobster roll. The first task for an arriving customer is to place an order and make payment with the cashier, which takes exactly 40 seconds to complete. If an arriving customer finds the cashier busy serving another customer, she waits in front of the cashier until the cashier is freed up. Seafood stir-fry and lobster roll are prepared in two separate stations, each with its own cook. After placing an order with the cashier, a customer moves to the station of her choice. If the cook is busy preparing lunch for another customer when the customer moves to the station, the customer waits in queue in front of the station until her turn; otherwise, she waits at the station until her