M1 has a mass of 5.070 kg. It is on a horizontal surface, connected by a massless thing to a hook where mass M2 can be increased smoothly. The pulley has a negligible mass and no friction. When M2 = 2.494 kg it begins to accelerate downwards at a rate of 1.887 m/s^2. calculate static friction - kinetic friction (static friction minus kinetic friction) between M1 and the surface.