16.5. A company has a central document-copying service. Arrivals are assumed to follow the Poisson probability distribution, with a mean rate of 15 per hour. Service times are assumed to follow the exponential distribution. With the present copying equipment, the average service time is 3 minutes. A new machine is available that will have a mean service time of 2 minutes. The average wage of the people who bring the documents to be copied is $8 an hour.