$3\mathrm{.}13.$ Queueing at Taco Terrace. A new fast food restaurant is opening in Middleville. The current plan to serve drive$-$up customers involves two servers. The first server window will take the customer's order with a mean service time of $38\mathrm{.}5$ seconds. The second server window will collect the money and give the order to the customer with a mean service time of $60\mathrm{.}5$ seconds. The expected arrival rate is $50$ drive$-$up customers per hour. The interarrival and departure time patterns have negative exponential distributions.

A$.$ If you neglect the "move$-$up$"$ time from the first window to the second, what is the average time a Taco Terrace drive$-$up customer will spend in the system?

B$.$ How many car lengths of space need to be provided between the two server windows such that, under "average" conditions, the first server window is not blocked by a back$-$up at the second window?