Please Help (Math)

Note  that the side of the square  = 5

Then, by symmetry,   the  radius  of  the circle  =  (1/2)  of this  =  2.5

So....the yellow region = 

Area of square - Area of circle  

5^2  -  pi (2.5)^2  =

[25  -  6.25 pi] ft^2   ≈ 5.4 ft^2