The following expression describes the serial$/$parallel precedence relationship among

six processes p$\_(1)$ through p$\_(6)$ :

P$($S$($P$($p$\_(3),$S$($p$\_(1),$P$($p$\_(6),$p$\_(5)))),$p$\_(2)),$p$\_(4))$

Transform this expression into a program using:

$($a$)$ cobegin$/$coend

$($b$)$ fork, join, quit primitives