A

$10$ secs$.$

$$6$

B

$30$ secs$.$

$7$

C

$60$ secs$.$

$7$

D

$40$ secs$.$

$7$

E

$30$ secs$.$

$7$

F

$20$ secs$.$

$8$

Refer to Exhibit $5-1.$ If an extra counter is added at the bottleneck location, how many customers can the cafeteria process in an hour?

$240$

$120$

$360$

$90$

$180$