Two chunks of rock, each having a mass of \(1.00 \mathrm{~kg}\), collide in space. Just before the collision, an observer at rest in the reference frame of a nearby star determines that rock \(\mathrm{A}\) is moving toward the star at \(0.500 c_{0}\) and rock \(\mathrm{B}\) is moving away from the star at \(0.300 c_{0}\). If the rocks stick together after the collision, what are the direction and magnitude of their velocity (in the reference frame of the star) immediately after the collision?