$(2$ points$)$ Use queueing theory.

National Bank is deciding how many drive$-$in teller windows to open on a busy Saturday. Manager Tod

Eschenbach estimates that customers arrive at a rate of $=16$ per hour and that each teller can service $=20$

customers per hour.

a$.$ What is the optimum number of teller window$($s$)$ to open if the manager wants the average number of

customers in line is less than $0\mathrm{.}05$ customers? $[$Use table D$\mathrm{.}5]$

b$.$ What is the average waiting time in the queue for the above optimum scenario $($in minutes$)?$