$1.$ The tellers $at$ a bank form a queueing system. Suppose there are $3$ tellers that have exponential distributions for service time with the same average service rate $of0\mathrm{.}5$ customers per minute. Let the customer arrival rate $be1\mathrm{.}2$ customers per minute. What $is$ the expected number $of$ customers waiting $in$ the queue using the approximate formula for multiple server queues?