Design a "bungee jump" apparatus for adults. a bungee jumper falls from a high platform with two elastic cords tied to the ankles. the jumper falls freely for a while, with the cords slack. then the jumper falls an additional distance with the cords increasingly tense. assume that you have cords that are 12 m long, and that the cords stretch in the jump an additional 19 m for a jumper whose mass is 120 kg, the heaviest adult you will allow to use your bungee jump (heavier customers would hit the ground).