From the given figure,
The length of one side of the square, a=5 ft.
The length of the side of the square is the same as the diameter of the circle.
Hence, the diameter of the circle, D=a=5 ft.
Now, the radius of the circle is,
The area of the circle(red region) is,
The area of the square is,
Now, the area of the yellow region can be found as,
Therefore, the area of the yellow region is 5.4 sq.ft.