This module simulates the process of customers arriving to a queueing system, waiting in a queue (if all the servers are busy), and then receiving service from one of the servers before departing when the service is completed. The customers arrive randomly, so the interarrival times (time between consecutive arrivals) have an exponential distribution. The mean arrival rate l can be chosen from the pull-down list "Arrival Rate". The service times have an exponential distribution, where the mean service rate m can be chosen from the pull-down list "Service Rate". Users also can select the number of servers from the pull-down list "NS".