The driver of a vehicle is following another vehicle in front of her on a two-lane highway at night. She keeps a clearance of one car length for every 4 mph of speed while she follows the lead car. However, while going downhill at 56 mph, the lead car crashes into the rear of an unlighted abandoned truck. At what speed will her car hit the wreckage? Assume a perception- reaction time is 2 seconds, a deceleration rate of 11.2 feet/sec?, the length of cars of 18 feet and the road grade as 3%.