Recall that the equilibrium $($optimal$)$ utilization gives us the point at which the excess capacity $\backslash$mu $-\backslash$rho $\backslash$mu equals the mean queue size $($average number in the queue$)$ E$[$Lq$].$ To help the grocery store manager, we can solve the optimal utilization $\backslash$rho $*$ in terms of s by expressing $\backslash$rho $*$ as $(\backslash$lambda $/$s$*)/\backslash$mu $,$ since each server is expected to take on $\backslash$lambda $/$s$*$ arrivals. What is this optimal staffing level s$*($number of servers$)?$ Considering any one of the individual s$*$ queues, derive the expected waiting time $($seconds$)$ spent in line for a customer.