A baby elephant is stuck in a mud hole. To help pull it out, game keepers use a rope to apply force a, as part a of the drawing shows. By itself, however, force a is insufficient. Therefore, two additional forces b and c are applied, as in part b of the drawing. Each of these additional forces has the same magnitude f. The magnitude of the resultant force acting on the elephant in part b of the drawing is twice that in part a. Find the ratio f/fa.