Two salesmen in an office are either on the phone or not.

Either salesmen is on the phone an exponential amount of time with And then off the phone an exponential amount of time with

Formulate a Markov chain model where the states indicate who is on the phone.

Find the stationary probabilities.

Suppose they upgrade their phone system so that a call to a busy line is forwarded to the other line and lost if the second line is busy. Find the new stationary probabilities.