Problem 11-03 (Algorithmic) 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 18 customers per hour or 0.3 customers per minute. In the same bank waiting line system, assume that the service times for the drive-up teller follow an exponential probability distribution with a service rate of 24 customers per hour, or 0.4 customers per minute. Determine the following operating characteristics for the system:

What is the average time a customer spends in the system. If required, round your answer to nearest whole number.