\(k{x_0} + \sigma \frac{L}{2}Ag = Mg\)
\(\left[ {mass = density \times volume} \right]\)
\( \Rightarrow k{x_0} = Mg - \sigma \frac{L}{2}Ag\)
\( \Rightarrow {x_0} = \frac{{Mg - \frac{{\sigma LAg}}{2}}}{k} = \frac{{Mg}}{k}\left( {1 - \frac{{LA\sigma }}{{2M}}} \right)\)
$\left( g =980 \,cm / s ^{2}\right)$