Block's colliding at some height!

Classical Mechanics Level 3

In a physics lab, a small cube slides down a friction-less incline as shown in figure, it strikes elastically and horizontally with another cube that is only one-half of its mass. If the incline is \(20 cm\) high and the table is \(90 cm\) off the floor, big and small cubes strikes the ground at a distance \(x\) & \(y\) meter respectively from the table . Then \(\large \frac{y}{x}\) equal to