First Local Bank would like to improve customer service at its drive-in facility by reducing waiting and transaction times. On the basis of a pilot study, the bank's process manager estimates the average rate of customer arrivals is 15 cars per hour. All arriving cars line up in front of a window and are served on a first-come, first-served basis. Each transaction requires on average 3 minutes to complete. Assume that the arrival of cars follows a Poisson process, and that the transaction times are exponentially distributed. The bank now has one window that serves the drive-in customers. It costs $20 an hour to staff this window. The customer relations (CR) manager estimates that the cost (loss of goodwill and future business, ete.) due to a customer's waiting in the queue has a linear form, i.e., the bank incurs a cost of 10 dollars per hour per customer in queue. On the other hand, as soon as a customer goes into service, the bank does not incur any goodwill loss. d) What is the probability that there are 3 customers in the system (including the ones waiting in line and the ones receiving service at the window)