$(1)$ Calculate average service time $($question C$).$ And then multiply average service time with flow rate $(50$ customer per hour$)$

$(2)$ Add the inventory $($number of customers$)$ at the following six stages of the service process:

$1.$ Number of customer waiting before initial review process

$2.$ Number of customer at the initial review process

$3.$ Number of customer waiting before the license process

$4.$ Number of customer at the license process

$5.$ Number of customer waiting before the title process

$6.$ Number of customer at the title process