9. When a family of four with a total mass of 650 kg step into their 1200-kg car, the car's springs compress 1.3 cm. What is the spring constant of the car's springs in N/m, assuming they act as a single spring? A) 12×102 B) 50 x103) C) 49 × 104) D) 90 x104) E) 14 x105)