A grocery store has three check-out counters. The average service rate for each check-out counter is 25 customers per hour. The average arrival rate is 60 customers per hour. Assuming it is a multiple-server waiting line model; determine the average number of customers waiting for a check-out counter and the average time a customer must wait for a check-out counter. What is the probability that there will be less than or equal to 4 customers in the system?