A shopping store is considering changing its checking out system. In the current system, store customers divide themselves equally between the lines that form in front of 5 store clerks. The manager is considering having customers wait in one line and then proceed to the next available clerk. If the service rate is 20 customers per hour and the average number of arrivals per hour is 75 customers, determine which system results in the lowest customer waiting time (the average time a customer spends waiting in the queue).

Hint: The current system consists of 5 single-server queues, but the proposed system is a multiple-server queue with 5 servers.