A Grocery store operates with 3 check-out counters. The manager uses the following schedule to determine the number of counters in operation, depending on the number of customers in line. Number of customers in store Number of counters in operation 1 to 3 4 to 6 More than 6 1 2 3 Customers arrive in the counters according to Poisson distribution with mean rate of 10/Hr. The average checkout per customer is exponential with mean 12 mins. Determine the expected number of idle counters.