Ball A is dropped from top of a building. At same instant ball B is thrown vertically upwards from ground. When the balls collide, they were moving in opposite directions and speed of A is twice the speed of B. At what fraction of the height of building did the collision occur

Question

\[(a)\;\frac{1}{3} \quad (b)\;\frac{2}{3} \quad (c)\;\frac{1}{4}\quad (d)\;\frac{2}{5}\]