A bungee jumper falls for $1\mathrm{.}8$ s before the bungee cord begins to stretch. Until the jumper has bounced back up to this level, the bungee causes the jumper to have an average acceleration upward of $6$ m$/$s$2.$

$($a$)$ How fast is the jumper going when the bungee cord begins to stretch?

m$/$s

$($b$)$ How far below the diving platform is the jumper at that moment?

m

$($c$)$ How long after the bungee cord begins to stretch does the jumper reach the low point of the drop?

s

$($d$)$ How far below the diving platform is the jumper at the instant the speed is zero?