A telephone exchange has two long distance operators.The telephone company find that during the peak load,long distance calls arrive in a poisson fashion at an average rate of 15 per hours.The length of service on there cala in approximately exponentially distributed with mean length 5 minutes.
a)what is the probability that a subscriber will have to wait for his long distance call during the peak hours of the day?
b)If the subscriber will wait and are served in turns,what is the expected waiting time?
c)Establish the formula used.