arrive at the rate of $4$ persons per hour, according to a Poisson distribution, and the accounts officer spends an average of $12$ minutes with each customer.

$1.$ Determine the operating characteristics for this system $($i$.$e$.,$ P$0,$ L$,$ Lq$,$ W$,$ Wq$).$

$2.$ Add an additional accounts officer to the system so that it is now a multiple$-$server queuing system with two channels and determine the operating characteristics.