2. In the B&K model of Example 15.5-1, suppose that the interarrival time at the checkout area is exponential with mean 5 minutes and that the checkout time per customer is also exponential with mean 10 minutes. Suppose further that B&K will add a fourth counter and that counters will open based on increments of two customers. Determine the following:

(a) The steady-state probabilities, PII for all n.

(b) The probability that a fourth counter will be needed.

(c) The average number of idle counters.