use X=2

A post office has two counters, the first one handles money-orders and registration letters, while the second handles all other businesses. It has been found that service time distributions for both the counters are exponential with a mean service time of four minutes per customer. The customers are found to arrive at the first counter in a Poisson fashion with a mean arrival rate of (7+X) per hour while the customers arrive at the second counter in a Poisson fashion with a mean arrival rate of (10+X) customers per hour. What would be the effect on the average waiting time for the two types of customers if each counter can handle all types of businesses