Suppose you place a coin on a book; the book’s cover acts as a ramp. You open the cover slowly until static friction is overcome. The coin begins to slide. What happens to the forces on the coin as the angle of the cover changes? Select all correct answers. a. A component of the frictional force begins pushing the coin and book together. b. The frictional force decreases suddenly as the coin starts to slide. c. The gravitational force increases. d. The component of gravitational force along the surface increases. e. The component of gravitational force perpendicular to the surface decreases. f. The normal force decreases slowly, which produces a slow decrease in static friction.