A 15.0-kg block is dragged over a rough, horizontal surface by a 70.0-N force acting at 20.0° above the horizontal. The block is displaced 5.00 m, and the coefficient of kinetic friction is 0.300. Find the work done on the block by a) The 70-N force, b) The normal force, and c) The gravitational force. D) What is the increase in internal energy of the block-surface system due to friction? E) Find the total change in the block's kinetic energy.