Willow Brook National Bank operates a drive-up teller window that allows customers to complete bank transactions without getting out of their cars. On weekday mornings, arrivals to the drive-up teller window occur at random, with an arrival rate of 15 customers per hour or 0.25 customers per minute.

Let's assume that the service times for the drive-up teller follow an exponential probability distribution with a service rate of 21 customers per hour, or 0.35 customers per minute.

Determine the following operating characteristics for the system. (Round your answers to four decimal places.)

(a)

The probability that no customers are in the system

(b)

The average number of customers waiting

(c)

The average number of customers in the system

(d)

The average time (in min) a customer spends waiting

min

(e)

The average time (in min) a customer spends in the system

min

(f)

The probability that arriving customers will have to wait for service