A 69.3-kg circus performer is fired from cannon that are elevated at an angle of 40.4° above the horizontal. The cannon uses strong elastic bands to propel the performer, much in the same way that a slingshot fires a stone. Setting up for this stunt involves stretching the bands by 3.03 m from their unstrained length. At the point where the performer flies free of the bands, his height above the floor is the same because the height of the net into which he is shot. He takes 2.24 s to travel the horizontal distance of 28.7 m among this point and the net. Ignore friction and air resistance and decide the effective spring constant of the firing mechanism.