A box full of books rests on a wooden floor. The normal force the floor exerts on the box is 236 N. (a) You push horizontally on the box with a force of 129 N, but it refuses to budge. What can you say about the coefficient of static friction between the box and the floor? ?s > (b) If you must push horizontally on the box with a force of at least 137 N to start it sliding, what is the coefficient of static friction? (c) Once the box is sliding, you only have to push with a force of 113 N to keep it sliding. What is the coefficient of kinetic friction?