Velocity after Elastic Collision!

Classical Mechanics Level 4

Two steel spheres, having radii \(a\) and \(2a\) are released from a height \(h\) as shown in figure. Assume that during motion the centers of the spheres lies on a vertical line. Larger sphere collides with the ground and recoils and collides with the small sphere. Collisions are perfectly elastic. Velocity of small sphere just after its collision is-