A ball of mass 3M moves with a velocity of V toward another stationary ball of mass 6M. Eventually, it collides elastically with the stationary ball and scatters at an angle of 90° with its initial direction of motion. The ball of mass 6M scatters at an angle of 30° with the direction of motion of 3M. Calculate the fraction of the initial kinetic energy of the ball of mass 3M that is transferred to the other ball after the collision. (Assume that there is no friction.)

• A. $\frac16$
• B. $\frac13$
• C. $\frac{1}{\sqrt3}$
• D. $\frac23$