In this thesis,we discuss how to solve the limiting probabilities for an m/m/c/k queue with second optional service by Gaussian Elimination and GMRES(Generalized Minimal RESidual) which is faster.
[4] YOUCEF SAAD’ AND MARTIN H. SCHULTZ(1986).“Gmres: a generalized minimal residual algorithm for solving nonsymmetric linear systems”,SIAM J. Sci. and Stat. Comput., 7(3), 856–869