5. A 1,250 kg-roller-coaster car shown in the figure below is pulled up to point 1 where it is released from rest. (Assume that there is no friction) (20 pts.] 35 m 15 ml a. What is the total mechanical energy of the roller-coaster car? b. Calculate the speed at point 2. c. Calculate the speed at point 3. d. Calculate the speed at point 4. 6. A 1-kg rock is dropped from a height of 6.0 m. At what height is the rock's kinetic energy twice its potential energy? (10 pts.)