B&K Groceries operates with three check-out counters. The manager uses the following sched- ule to determine the number of counters in operation, depending on the number of customers in store: No. of customers in store No. of counters in operation 1 to 3 4 to 6 More than 6 Customers arrive in the counters area according to a Poisson distribution with a mean rate of 10 customers per hour. The average check-out time per customer is exponential with mean 12 minutes 3. In the B&K model of Example 15.5-1, suppose that all three counters are always open and that the operation is set up such that the customer will go to the first empty counter. Determine the following: (a) The probability that all three counters will be in use. (b) The probability that an arriving customer will not wait.