Answer:
86 ft^2
Explanation:
The square is 20 by 20 units and the circle has a diameter of 20 units.
The shaded area is (area of the square) - (area of the circle), or
A = 400 units^2 - 3.14(10)^2 units^2, or:
= 400 units^2 - 314 units^2
= 86 ft^2 (matches the last of the given possible answers)