Forces and equilibrium — practice question

Two small blocks $A$ and $B$ are kept at rest on a smooth plane that is inclined at $30^\circ$ to the horizontal. Each block is maintained in equilibrium by a force of magnitude $18\,\text{N}$. For $A$, the force acts up the plane, parallel to a line of greatest slope; for $B$, the force acts horizontally in the vertical plane containing a line of greatest slope (see diagram).