Representation of data — practice question

The diameter $AB$ of a uniform semicircular lamina is $0.8\text{ m}$. The lamina is placed in a vertical plane, with point $B$ touching a rough horizontal surface and $A$ positioned vertically above $B$. A force of magnitude $6\text{ N}$ acting in the plane of the lamina is applied at $A$ at an angle of $20^\circ$ below the horizontal, and this keeps the lamina in equilibrium.