You have been hired to design a spring-launched roller coaster that will carry two passengers per car. the car goes up a 13-m-high hill, then descends 20 m to the track's lowest point. you've determined that the spring can be compressed a maximum of 2.5 m and that a loaded car will have a maximum mass of 420 kg. for safety reasons, the spring constant should be 12 % larger than the minimum needed for the car to just make it over the top. a)what spring constant should you specify? b)what is the maximum speed of a 320 kg car if the spring is compressed the full amount?