7.11 Consider a birth-and-death process representing a multiserver finite population system with the following birth and death rates: λk 5 ð4 2 kÞλ k 5 0; 1; ...; 4 μk 5 kμ k 5 1; ...; 4

a. Find, in terms of λ and μ, pk, the probability that there are k customers in the system, k 5 0; 1; ...; 4.

b. Find the average number of customers in the system.