A dry cleaner has a single drive-thru window for customers. The arrival rate of cars follows a Poisson distribution the service time follows an exponential distribution The average arrival rate is 16 per hour and the average service time three minutes (a) What is the average number of cars in the line? (b) What is the average time spent waiting to get to the service window () What percentage of time is the dry cleaner's drive-thru window idle? (d) What is the probability there are more than 2 cars at the drive-thru window (e) if a new window is added , find the average time spent waiting ? ( )