A tightrope walker who weighs 640 N walks along a steel cable. When he is halfway across, the cable makes an angle of .040 rad below the horizontal. (a) What is the strain on the cable? Assume the cable is horizontal with a tension of 80 N before he steps onto it. Ignore the weight of the cable itself. (b) What is the tension in the cable when the tightrope walker is standing at the midpoint? (c) What is the cross-sectional area of the cable? (d) Has the cable been stretched beyond its elastic limit (2.5x10^8 Pa)?