A 60 kg student rides on a roller coaster that makes a vertical loop. a). Draw a free-body diagram for when the student is at the bottom of the loop. b). If the radius of the loop is 30 m, and the roller coaster is traveling at 20 m/s at the bottom of the loop, what is the net force acting on the student in the vertical direction? c). What force does the seat apply to the student when at the bottom of the loop?