25. Customers arrive at a service station, manned by a single server who serves at an exponential rate μ1, at a Poisson rate λ. After completion of service the customer then joins a second system where the server serves at an exponential 26. Consider an ergodic M/M/s queue in steady state (that is, after a long time)

and argue that the number presently in the system is independent of the sequence of past departure times. That is, for instance, knowing that there have been departures 2, 3, 5, and 10 time units ago does not affect the distribution of the number presently in the system.