A $6\mathrm{.}00-$g bullet has a muzzle velocity of $210$ m$/$s when fired by a rifle with a weight of $25\mathrm{.}0$ N$.$

$($a$)$ Determine the recoil speed of the rifle.

m$/$s

$($b$)$ If a marksman with a weight of $650$ N holds the rifle firmly against his shoulder, determine the recoil speed of the shooter and rifle.

m$/$s