A2. A block weighing 80N rests on a plane inclined at 20 to the horizontal. The coefficient of static friction is 0.25, while the coefficient of kinetic friction is 0. 15. 209 a) What is the minimum force | F|, parallel to the plane, that will prevent the block slipping down the plane? [2 points] b) What is the minimum force | F| that will start the block moving up the plane? [2 points] c) What force |F| is required to move the block up the plane at constant speed? [1 point]