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 bank's 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 the transaction. Assume that both interarrival and activity times are exponentially distributed.

The manager estimates the cost of a customer's 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-speed 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.

How long does it take a teller to process a customer - its unit load (hours/unit)?

What is the 4 teller resource pool processing capacity (units/hour)?

What is the process throughput (units/hour)?

What is the 4 teller resource pool utilization(%)?

What is the approximate average queue length (customers)?

What is the expected average wait time per customer (minutes)?

What is the expected average total time for customers in the system (minutes)?

What is the expected hourly waiting cost?

What is the expected hourly total cost?