A helium atom $($mass $4\mathrm{.}00$ u$)$ moving at $616$ m$/$s to the right collides with an oxygen molecule $($mass $32\mathrm{.}0$ u$)$ moving in the same direction at $419$ m$/$s$.$ After the collision, the oxygen molecule moves at $456$ m$/$s to the right. What is the velocity of the helium atom after the collision? Assume$$the positive direction to be to the right. If the direction of velocity is toward$$right$,$ enter a positive value and if the direction of velocity is toward$$left$,$ enter a negative value.