Customers arrive at a bank drive-up window every 6 minutes based on a Poisson distribution. Once they arrive at the teller, service time is exponentially distributed based on a rate of 5 minutes per transaction,
a. What is the probability that 3 or fewer customers will arrive in one hour?
b. How many customers are most likely in line (waiting) at any one point in time?
c. What will be the average time waiting in the system?
d. What will be the average time in the system?