A block having mass $\mathrm{M}$ is placed on a horizontal frictionless surface. This mass is attached to one end of a spring having force constant $\mathrm{k}$. The other end of the spring is attached to a rigid wall. This system consisting of spring and mass $\mathrm{M}$ is executing SHM with amplitude $\mathrm{A}$ and frequency $\mathrm{f}$. When the block is passing through the mid-point of its path of motion, a body of mass $\mathrm{m}$ is placed on top of it, as a result of which its amplitude and frequency changes to $\mathrm{A}^{\prime}$ and $\mathrm{f}$.
If the velocity before putting the mass and after putting it is $\mathrm{v}$ and $\mathrm{v}^{1}$ respectively, then $\left(\mathrm{v}^{1} / \mathrm{v}\right)=\ldots \ldots \ldots \ldots$
(A) $\{\mathrm{M} /(\mathrm{m}+\mathrm{M})\}$
(B) $\{(\mathrm{M}+\mathrm{m}) / \mathrm{M}\}$
(C) $\{(M+m) /(M-m)\}\left(A^{1} / A\right)$
(D) $\{(M-m) /(M+m)\}\left(A^{1} / A\right)$