RideShare offers short-term rentals of vehicles that are kept in small lots in urban neighborhoods with plenty of potential customers. With one lot, it has ten cars. The interarrival time of potential demand for this lot from its base of customers is 20 minutes. The average rental period is 4 hours. If a customer checks avallability of vehicles in this lot online and finds that they are all rented for the desired time, the customer skips renting and finds alternative arrangements. However, because customers pay a monthly fee to subscribe to this service, RideShare does not want customers to be disappointed too often