IIT JEE Advanced 2010 Paper 1

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 P1 = mg (sin θ - m cos θ) to P2 = (sin θ + m cos θ), the frictional force f versus P graph will look like