a block is pulled across a rough, horizontal surface from point a to point b by a force, p as shown in the figure. the magnitude of the force of friction acting on the block between a and b is 1.2 n, and points a and b are 0.75 m apart. if the kinetic energies of the block at a and b are 4.2 j and 5.8 j, respectively, how much work is done on the block by the force p between a and b?