At some hight h = 1.7 m, a mini roller coaster of mass 2.4 kg starts to fall from rest. It then loops through a circular path of radius R = 0.45 m (see figure). Ignore all kinds of friction, and take g = 9.81 m/s^2. 

(a) Find the speed of the roller coaster when it goes across the top of the circle (point A) (in m/s).

 (b) Find the magnitude of the normal force (in newtons) that the rail exerts on the roller coaster when it goes across the bottom of the circle (point B) 

 (c) Find the minimum height h (in m) so that the roller coaster can pass the circle path without falling out of it.

h