Designers of today’s cars have built “5mi/h (8km/h) bumpers” that are designed to compress and rebound elastically without any physical damage at speeds below 8km/h. IF the material of the bumpers permanently deforms after a compression of 1.5cm, but remains like an elastic spring up to that point, what must the effective spring stiffness constant of the bumper be, assuming the car has a mass of 1300kg and is tested by ramming into a solid wall?