A plate of mass M remains in equilibrium in air when n bullets are fired per second on it. The mass of each bullet is m and it strikes the plate with speed v' If the coefficient of restitution is e, then (M>>m) 

• A

  $\mathrm{M}=\frac{\mathrm{nm}(1+\mathrm{e})\mathrm{V}}{\mathrm{g}}$

• B

  $\mathrm{M}=\frac{\mathrm{nmv}}{\mathrm{g}}$

• C

  $\mathrm{M}=\frac{2\mathrm{nm}\left(\mathrm{e}+{\mathrm{e}}^2\right)}{\mathrm{g}}$

• D

  $M=2n\mathrm{mg}$