How long does the average customer wait in line $($in minutes$)?$An urban post is set up to have customers join a single line which is served by multiple workers. $30$ customers arrive per hour $($ca $=0\mathrm{.}92)$ during lunch and join a single line which is served by $5$ clerks. It takes about $7$ minutes to serve each customer $($cp $=0\mathrm{.}37).$ How long does the average customer wait in line $($in minutes$)?$