35,141.576 square feet is the answer I got. I drew two arbitrary polylines either side of the variable width one, and pick point hatched the area enclosed either side of it, added the area of the hatches. Then I deleted the variable width polyline, hatched the entire area enclosed by the two arbitrary polylines, subtracted the area of the two initial hatches, the answer is the area of the variable width polyline. There are beginning and end segments of the pline that don't have variable width, I disregarded them.

Imperial measurements are rubbish. Why did the hatches' area get reported in them? 3264.759240791 m² is the conversion.