\(P_{ij} (t+h)=\sum h \enspace \mu_{ik}\enspace P_{kj}(t) + (1 + h \enspace \mu_{ii})\enspace P_{ij}(t) + o(h)\) On Rhs how the term \((1 + h \enspace \mu_{ii})\enspace P_{ij}(t)\) comes? Reference solution to question 5.10, page 55 of chap 5