Forces and equilibrium — practice question

A block with mass $11\,\text{kg}$ is initially stationary on a rough plane that is inclined at $30^\circ$ to the horizontal. A force is applied to the block up the plane, along a line of greatest slope. When the force has magnitude $2X\,\text{N}$, the block is just about to move down the plane, and when the force has magnitude $9X\,\text{N}$, the block is just about to move up the plane.