Aggie Hotdogs has one drive$-$through window. An average of $40$ customers per hour arrive at

the window. It takes an average of $1\mathrm{.}2$ minutes to serve a customer. Assume that interarrival

and service times are exponential.

a$.$ On average, how many customers are waiting in line?

b$.$ On average, how long does a customer spend at the restaurant $($from time of arrival to

time service is completed$)?$

c$.$ What fraction of the time are more than $3$ cars waiting for service $($this includes the car $($if

any$)$ at the window$)?$