Consider an espresso stand with a single barista. Customers arrive to the stand at the rate of $28$

per hour according to a Poisson distribution. Service times are exponentially distributed with a

service rate of $35$ customers per hour. The average number of customers in the system $($i$.$e$.,$

waiting and being served$)$ is

$4\mathrm{.}0.$

$3\mathrm{.}8.$

$2\mathrm{.}0.$

$3\mathrm{.}2.$