QSO-310 Management of Service Ops

A business school is considering replacing its copy machine with-a faster model. Past records show that the average student arrival rate is 24 per hour, Poisson distributed, and that the service times are distributed exponentially. The selection committee has been instructed to consider only machines that will yield an average turnaround time (i.e., expected time in the system) of 5 minutes or less. What is the smallest processing rate per hour that can be considered?

There's no information missing (above is the whole question) Capacity Planning and Queuing Models