A 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 banks process manager estimates the average rate of customer arrivals at 30 cars per hour. All arriving cars line up in a single lane and are served at one of 4 windows on a first-come-first-served basis. Each teller currently requires an average of 6 minutes to complete a transaction. Assume that both interarrival and activity times are exponentially distributed. The manager estimates the cost of a customers waiting time in queue (in terms of future business lost to the competition) to be $20 per customer per hour.

A casual study of the competition indicates that a customer should be in and out of a drive-in facility within an average of 8 minutes (including waiting). The bank is considering the possibility of leasing high-speeds information retrieval and communication equipment that would cost $30 per hour. The new equipment would, however, serve the entire facility and reduce each teller's transaction processing time to an average of 4 minutes per customer.

The bank is also considering the possibility of leasing high-speed information equipment and reducing the number of tellers to 3.

a. What is the expected average total time per customer in the system (minutes)? Average Total Time=Waiting time + Processing time= Ti+Tp

b. What is the expected hourly waiting cost ($)? Hourly waiting cost = average queue length * hourly cost per customer

c. What is the expected hourly total cost ($)? Hourly total cost= waiting cost +equipment cost