Step-by-step explanation:
The force of the roller-coaster track on the cart at the bottom is given by :
, m is mass of roller coaster
Case 1.
R = 60 m v = 16 m/s

Case 2.
R = 15 m v = 8 m/s

Case 3.
R = 30 m v = 4 m/s

Case 4.
R = 45 m v = 4 m/s

Case 5.
R = 30 m v = 16 m/s

Case 6.
R = 15 m v =12 m/s

Ranking from largest to smallest is given by :
F>E>A=B>C>D