A Bullet (Mass = M)is Fired at Speed V into a Block

Multiple Choice

A bullet (mass = m) is fired at speed V into a block of mass M (with M>m) which is hanging vertically from a light string of length L.The bullet stops in the block.If the recoiling block + bullet system reaches a height of 2/3L,then the initial speed of the bullet is given by

A) M $\times$ (1gL/3) ^1/2/m
B) M $\times$ (2gL/3) ^1/2/m
C) M $\times$ (3gL/4) ^1/2/m
D) m $\times$ (4gL/3) ^1/2/M
E) M $\times$ (4gL/3) ^1/2/m