The semiaxes are 170/2 = 85 ft and 40/2 = 20 ft. The equation of the ellipse is+ = 1. From the equation, y = +/- . Substitute here x = 85-10 = 75. Then y = +/- = +/- 9.412 (rounded to 3 decimal places). So, the answer to the problem's question is 9.412 - (-9.412) = 2*9.412 = 18.824 ft (rounded). ANSWER