First, let's start with the easy portion, the rectangle. To solve for area, you would multiply, Length × Width
26 ft × 20 ft = 520 ft
Next, you would solve for the semi-circle. The equation would be, A = πr²
314.16 = πr²
Now, you would divide the area of the circle by two.
314.16 ÷ 2 = 157.08
The last step would be to add the area of the rectangle and the area of the semi-circle.
520 + 157.08 = 677.08
Your answer would be 677.08 ft²
Sorry to post this so late, I had to go somewhere.
I hope this helps!