Q$2($QUEUING$)-$ A pizza place is considering opening a drive$-$through window for customer pickups. It is estimated that at peak times $(6-9$pm and $1-3$am$),$ customers will arrive at a rate of $20$ per hour. The worker who will staff the window can serve customers at the rate of one every $2\mathrm{.}8$ minutes. For the peak times, what is the: