# Question

Consider the single-server variation of the nonpreemptive priorities model presented in Sec. 17.8. Suppose there are three priority classes, with λ1 = 1, λ2 = 1, and λ3 = 1. The expected service times for priority classes 1, 2, and 3 are 0.4, 0.3, and 0.2, respectively, so μ1 = 2.5, μ2 = 3 1/3, and μ3 =] 5.

(a) Calculate W1, W2, and W3.

(b) Repeat part (a) when using the approximation of applying the general model for nonpreemptive priorities presented in Sec. 17.8 instead. Since this general model assumes that the expected service time is the same for all priority classes, use an expected service time of 0.3 so μ = 3 1/3. Compare the results with those obtained in part (a) and evaluate how good an approximation is provided by making this assumption.

(a) Calculate W1, W2, and W3.

(b) Repeat part (a) when using the approximation of applying the general model for nonpreemptive priorities presented in Sec. 17.8 instead. Since this general model assumes that the expected service time is the same for all priority classes, use an expected service time of 0.3 so μ = 3 1/3. Compare the results with those obtained in part (a) and evaluate how good an approximation is provided by making this assumption.

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