As shown in figure, a spring attached to the ground vertically has a horizontal massless plate with a $2 \mathrm{~kg}$ mass in it. When the spring (massless) is pressed slightly and released, the $2 \mathrm{~kg}$ mass, starts executing S.H.M. The force constant of the spring is $200 \mathrm{Nm}^{-1}$. For what minimum value of amplitude, will the mass loose contact with the plate? (Take $\left.\mathrm{g}=10 \mathrm{~ms}^{-2}\right)$
(A) $10.0 \mathrm{~cm}$
(B) $8.0 \mathrm{~cm}$
(C) $4.0 \mathrm{~cm}$
(D) For any value less than $12.0 \mathrm{~cm}$.