A roller-coaster car speeds down a hill past point A and then rolls up a hill past point B. The car has a speed of 20.0 m/s at point A. If the track...

A roller-coaster car speeds down a hill past point A and then rolls up a hill past point B.a. The car has a speed of 20.0 m/s at point A. If the track exerts a normal force on the car of 2.06x10^4 N at this point, what is the mass of the car? (Be sure to account for gravitational force)b. What is the maximum speed the car can have at point B for the gravitational force to hold it on the track?In the diagram, A is a low point with radius 10.0 m and B is a high point with radius 15.0 m.