Willow Brook National bank operates a drive-up teller window that allows customers to complete bank transactions without getting out of their cars. On weekday mornings, arrivals to the drive-up teller window occur at random with a Poisson distribution with arrival rate of 20 customers per hour. (All applicable formulas are required) 1). how much is the mean number of arrivals per minute? the arrival rate . Assume that the service times for the drive-up teller follow an exponential probability distribution with a service rate of 30 customers per hour. 2) how much is the mean number of customers that can be served per minute? the service rate . 3) The probability that no customers are in the system 4) The average number of customers waiting 5) The average number of customers in the system 6)the average time a customer spends waiting 7) The average time a customer spends in the system 8) The probability that arriving customers will have to wait for service. 9) The probability that 3 customers in the system