Consider the queueing model with a preemptive priority queue discipline presented in Sec. 17.8. Suppose that s = 1, N = 2, and (λ1 + λ2) < μ and let Pij be the steady-state probability that there are i members of the higher-priority class and j members of the lower-priority class in the queueing system (i = 0, 1, 2, . . . ; j = 0, 1, 2, . . .). Use a method analogous to that presented in Sec. 17.5 to derive a system of linear equations whose simultaneous solution is the Pij. Do not actually obtain this solution.