$$A $1\mathrm{.}98-$kg particle has a velocity $(1\mathrm{.}992\mathrm{.}94)$ m$/$s$,$ and a $2\mathrm{.}93-$kg particle has a velocity $(1\mathrm{.}05+5\mathrm{.}99)$ m$/$s$.$

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

$+$

m$/$s

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