Suppose two asteroids strike head on$.$ Asteroid A $($mA $=7\mathrm{.}5$X$1012$ kg$)$ has velocity $3\mathrm{.}3$km$/$s before the collision, and asteroid B $($mB $=1\mathrm{.}45$X$1013$ kg$)$ has velocity $1\mathrm{.}4$ km$/$s before the collision in the opposite direction. If the asteroids stick together, what is the velocity of the new asteroid after the collision?