819 EXAMPLE 10.10-3 A library wants to improve its service facilities in terms of the waiting time of its borrowers, The library has two counters at present and borrowers arrive according to Poisson distribution with arrival rate / every 6 minutes and service time follows exponential distribution with a mean of 10 minutes. The library has relaxed its membership rules and a substantial increase in the number of borrowers is expected. Find the number of additional counters to be provided if the arrival rate is expected to be wice the present value and the average waiting time of the borrowers must be limited to half the present value