A body is in equilibrium under the influence of a number of forces. Each force has a different line of action. The minimum number of forces required is

A uniform disc is rolling on a horizontal surface. At a certain instant $\mathrm{B}$ is the point of contact and $\mathrm{A}$ is at height $2\mathrm{R}$ from ground, where $\mathrm{R}$ is radius of disc

The moment of inertia of a thin square plate $\mathrm{ABCD}$, of uniform thickness about an axis passing through the centre $\mathrm{O}$ and perpendicular to the plane of the plate is ( where ${\mathrm{I}}_1,{\mathrm{I}}_2,{\mathrm{I}}_3$ and ${\mathrm{I}}_4$ are respectively moments of inertia about axis $1,2,3$ and $4$ which are in the plane of the plate)