Suggest a call center in which calls arrive according to the Poisson procedure with rate L=30/hr. Suppose that there are two operators handling three phone lines. But, the second operator only works when all three lines are busy. Suppose that the service times for either operator are independent identically distributed exponential random variables with the mean of 4 minutes. Also, suppose that the arrival process and the service procedure are independent. Determine the long run probability that both operators are busy?