a 20-lb rests on a plane that is inclined at 30° above the horizontal. the height of the plane increases from left to right. the gravitational force acting on the block is make an illustration and work with 2-d vectors to answer the following: (a) what is a unit vector that points down the plane (parallel to the plane)? call (b) what is the force vector f (the magnitude of f is 20 lbs, the weight of the block.) (c) how much of f points in a direction that is parallel to the plane? compute this as the orthogonal projection of f onto ü. (d) how much of f points in a direction that is normal to the plane? compute this as n = f-proj f