John (whose line of sight is g ft above horizontal) is trying to estimate the height of a tall oak tree. He first measures the angle of elevation from where he is standing as 30 degrees. He walks 20 feet closer to the tree and finds that the angle of elevation has increased by 10 degrees. Estimate the height of the tree rounded to the nearest whole number.
A. 37 ft B. 64 ft C. 43 ft D. 72 ft

I got 64 ft, but my teacher got 43 ft. Did I do something wrong?