Restaurant $3($a$)$

Consider a process within a restaurant, which requires two employees. A customer enters the restaurant, and employee A fills the plate. It takes $5$ minutes for employee A to do that. Next, employee B accepts payment. It takes $2$ minutes for employee $B$ to do that. You can check that the process capacity is $12$ customers$/$hour$.$ If the demand rate is $10$ customers$/$hour$,$ what is the throughput rate of the system?