Forces and equilibrium — practice question

A particle $P$ with mass $0.5\text{ kg}$ is at rest on a rough plane inclined at angle $\alpha$ to the horizontal, where $\sin \alpha = 0.28$. A force of magnitude $0.6\text{ N}$, applied upwards to $P$ at angle $\alpha$ to a line of greatest slope of the plane, is just enough to stop $P$ from sliding down the plane.