A bullet of mass ‘m’ and velocity ‘a’ is fired in to a large block of wood of mass ‘M’. The final velocity of the system is:

A

$$\frac{Ma}{(m+M)}$$

B

$$\frac{(m+M)a}{M}$$

C

$$\frac{ma}{(m+M)}$$

D

$$\frac{(m+M)a}{m}$$