Which of the following arguments are of the form $($r $$ s$),$ r $\backslash$ s$?$

$($a$)($P $$Q$),$P $\backslash$ Q

$($b$)($P $$Q$),$ P $\backslash$Q

$($c$)($P $$ Q$),$ P $\backslash$ Q

$($d$)($P $($Q $$ R$)),$ P $\backslash ($Q $$ R$)$

$($e$)(($P v Q$)$ R$),$ P $\backslash ($Q v R$)$