A 2.30 kg block is initially at rest on a horizontal surface. A horizontal force F of magnitude 5.52 N and a vertical force P are then applied to the block (see the figure). The coefficients of friction for the block and surface are Us = 0.4 and JK = 0.25. Determine the magnitude of the frictional force acting on the block if the magnitude of P is (a)8.00 N and (b) 11.0 N. (The upward pull is insufficient to move the block vertically.)