Travelers arrive at the main entrance door of an airline terminal. There are two types of customers regular and frequent flier. The time between arrivals of regular customers is exponentially distributed with a mean of 2 minutes. The time between arrivals of frequent fliers is also exponentially distributed with a mean of 4 minutes. At the check in counter, travelers wait in a single line until one of the five agents is available to serve them. The check in time follows a regular distribution.