9 An average of 40 students per hour arrive at the MBA computing lab. The average student uses a computer for 20 minutes. Assume exponential interarrival and service times.

a If we want the average time a student waits for a PC to be at most 10 minutes, how many computers should the lab have?

b If we want 95% of all students to spend 5 minutes or less waiting for a PC, how many PCs should the lab have?