A block of mass \( M \) placed inside a box descends vertically with acceleration ‘\( a \)’. The block exerts a force equal to one-fourth of its weight on the floor of the box. The value of ‘\( a \)’ will be:
\( \frac{g}{4} \)
\( \frac{g}{2} \)
\( \frac{3g}{4} \)
\( g \)