Trucks using a single server loading dock have a mean arrival of $8$ per day. The loading$/$unloading rate is u$=9$ per day.

The cost of operating the unloading$/$loading server is u$ per hour and the cost of a truck waiting at rhe facility is $$1$ per truck per hour $($including the truck being served$)$

A$)$ calculate the total cost per hour

B$)$ propose a service rate u that minimizes the cost in part a$.$