$15\mathrm{.}9($A$)$ Production rate for a certain assembled product is $40$ units$/$hr$.$ The assembly work con$-$

tent time $=51$min. The line operates at $95\%$ uptime. Ten workstations have two workers on

opposite sides of the line so that both sides of the product can be worked on simultaneously.

The remaining stations have one worker. Repositioning time lost by each worker is $0\mathrm{.}15mi\frac{n}{?}$

cycle. It is known that the number of workers on the line is two more than the number

required for perfect balance. Determine $($a$)$ number of workers, $($b$)$ number of workstations,

$($c$)$ balance efficiency, and $($d$)$ average manning level $($ignore utility workers$).$