A $1\mathrm{.}96-$kg particle has a velocity $(1\mathrm{.}902\mathrm{.}90)$ m$/$s$,$ and a $2\mathrm{.}91-$kg particle has a velocity $(1\mathrm{.}04+6\mathrm{.}03)$ m$/$s$.$

$($a$)$ Find the velocity of the center of mass.

$+$

m$/$s

$($b$)$ Find the total momentum of the system.

$+$

kg $$ m$/$s