A bullet of mass $10\text{g}$ moving horizontally with a velocity of $400{\text{ms}}^{-1}$ strikes a wooden block of mass $2\text{kg}$ which is suspended by a light inextensible string of length $5\text{m}$. As a result the centre of gravity of the block is found to rise a vertical distance of $10\text{cm}$. The speed of the bullet after it emerges out horizontally from the block will be:

1. A
   $160{\text{ms}}^{-1}$
2. B
   $100{\text{ms}}^{-1}$
3. C
   $80{\text{ms}}^{-1}$
4. D
   $120{\text{ms}}^{-1}$