A quick-service restaurant has a single drive-through lane with one worker at the window. It is assumed that the worker can process an order every 4 minutes on average and that the processing (service) times are exponentially distributed. If customers arrive at the drive-through at the rate of 10 per hour, calculate the following service operation performance characteristics:
a. Percentage of time the worker at the drive-through is busy
b. Average number of cars waiting at the drive-through
c. Number of cars, on average, in the drive-through system
d. Average time a car spends waiting in the drive-through
e. Time, on average, spent in the drive-through system