Body A of mass 4m moving with speed u collides with an other body B of mass 2m, at rest. The collision is head on and elastic in nature. After the collision the fraction of energy lost by the colliding body A is :

A

$$\frac {8}{9}$$

B

$$\frac {4}{9}$$

C

$$\frac {5}{9}$$

D

$$\frac {1}{9}$$