The force required to keep a car from skidding in a turn varies jointly with the mass of the car m, the square of its speed v, and the curvature k of the turn. The curvature is the reciprocal of the radius of the turn, k=1/r. Suppose it takes 2800 lb of force to keep an 1800-lb car from skidding at 45 mi/h on a curve with radius 425 ft. What force is needed to keep the car from skidding at 50 mi/h on a curve with a radius of 440 ft?