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

Either salesmen is on the phone an exponential amount of time with mean \mu = 3. And then off the phone an exponential amount of time with rate \lambda = 1.

Formulate a Markov chain model \{0,1,2,12\} where the states indicate who is on the phone.

(a)Find the stationary probabilities.
(b)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.