The force needed to keep a car from skidding on a curve varies inversely as the radius of the curve and jointly as the weight of the car and the square of the
car's speed. Suppose that 400 pounds of force keeps a 1600-pound car from skidding on a curve of radius 800 ft at 50 mph. What force would keep the same
car from skidding on a curve of radius 600 ft at 60 mph?