Past exam of the mathematics course of the University of Cambridge / 2007 / ii / Paper 4 / 26J / a / Solution

The nonzero off-diagonal rates arewith a transition involving a negative coordinate omitted. These represent arrival, the two metamorphoses, and death. The diagonal generator entry is consequently $-(\lambda +\mu (c+r+b))$, so the holding rate is $\lambda +\mu n$.