The area of the square is 14*14 = 168 ft^2.
The area of the circle is πr^2. The radius is diameter/2 = 7. The area of the circle is 3.14*(7)^2 = 3.14*49 = 153.86 ft^2.
The area of the shaded part is the area of the square minus the area of the circle = 168 - 153.86 = 14.14 ft^2.
