(Bank Teller) One teller has been serving all customers at a local bank branch in a small town of Boston. Customers arrive in a mean of 1/15 hours (or 4 minutes) with a standard deviation of 1/15 hours. The teller spends a mean of 1/20 hours (or 3 minutes) with a standard deviation of 1/20 hours. Customers visit the branch for different tasks, which creates the variability of service times. Some of their requests, such as money withdrawals, take a short time whereas others such as foreign money deposits take long.
(Bank Teller)
(a) Use the average flow time (W) to calculate the average waiting time (Wq). [Answer format: two decimal places] (Hint: average flow time (W) = average waiting time (Wq) + mean service time (ts))
(b) Then use Little's law to calculate the average number of customers (Lq) waiting in line. [Answer format: two decimal places] (Hint: Lq includes only customers waiting in line, but not those being served. Little's law can be applied not only to an entire queue but also to the waiting line.)