89.
In order to calculate the net force acting from B to C, we need to consider the centripetal force, since the car is in a circular movement.
The centripetal force is given by:
Where ac is the centripetal acceleration, v is the linear speed and r is the radius of the curve.
So, for m = 1000, v = 20 and r = 100, we have:
Therefore the net force acting is 4000 N.