Determine the required height h of the roller coaster so that when it is essentially at rest

Question:

Determine the required height h of the roller coaster so that when it is essentially at rest at the crest of the hill A it will reach a speed of 100 km/h when it comes to the bottom B. Also, what should be the minimum radius of curvature ρ for the track at B so that the passengers do not experience a normal force greater than 4mg = (39.24m) N? Neglect the size of the car.