Laws of Motion

A block of mass m is on an inclined plane of angle θ. The coefficient of friction between the block and the plane is μ and tan θ > μ. The block is held stationary by applying a force P parallel to the plane. The direction of force pointing up the plane is taken to be positive. As P is varied from P 1 = mg(sinθ − μ cosθ) to P 2 = mg(sinθ + μ cosθ), the frictional force f versus P graph will look like