booking_clerkMC: A function to simulate the harassed booking clerk Markov chain.
Description
Simulates the harassed booking clerk Markov chain with given arrival and service rates up to t.end. The state space is (C(t),X(t),Y(t)), where C(t) represents the status of the clerk, X(t) the number of people waiting, and Y(t) the number of calls waiting. C(t) is 0 if clerk is idle, 1 if clerk is serving a person and 2 if clerk is serving a call.