Twenty-five percent of complainants who leave the USPS complaints department stop off

at a nearby caf (assume that the distribution of inter-arrival times to the caf is

exponential). Hungry complainants are the sole source of traffic for the cafe, who can

serve customers at an average rate of one customer every 10 minutes. Service times have

a standard deviation of 6 minutes.

c.

[1] Draw a process flow diagram of the USPS/caf system. Label it average service

rates and interarrival rates.

d.

[1] What is arrival distribution to the caf? What is its squared coefficient of

variation?

e. [3] On average, how many customers in the cafe are either being served or waiting in

line?