Boaty Boat is a motorboat rental shop located in Maine, which rents out motorboats to tourists visiting nearby national parks. When a customer requests to rent a motorboat and no motorboats are available (they are either with other customers or being cleaned for rental), the customer waits until a motorboat is available. Once a motorboat is rented out to a customer, the customer keeps it for an average of 45 minutes. Upon return, the motorboat is cleaned and tuned up, which takes about 15 minutes. Suppose BoatyBoat has 7 motorboats, and the demand for motorboat rental is 6.3 per hour. 

What is the average amount of time a customer waits to receive a motorboat?