$4.$ Elastic collisions in one dimension: A $620-$g object traveling at $2\mathrm{.}1$ m$/$s collides head$-$on with a $320-$g object traveling in the opposite direction at $3\mathrm{.}8$ m$/$s$.$ If the collision is perfectly elastic, what is the change in the kinetic energy of the $620-$g object?A$)$ It loses $0\mathrm{.}23$ J$.$B$)$ It gains $0\mathrm{.}69$ J$.$C$)$ It loses $0\mathrm{.}47$ J$.$D$)$ It loses $1\mathrm{.}4$ J$.$