A $2200-$kg auto moving northward at $12\mathrm{.}0$ m$/$s runs into a $3800-$kg truck which is also moving northward, but at $5\mathrm{.}00$ m$/$s$.$ If the vehicles lock bumpers, how fast are they moving just after the collision?

hint: Its a hit and stick situation but the velocities have the same sign before collision. After the move with the same velocity $($m$1+$m$2)$V$\text{'}=$ momentum after

$1.$

Group of answer choices

$12$m$/$s

$-5$m$/$s

$7\mathrm{.}57$ m$/$s

$3\mathrm{.}57$m$/$s