Area of a Square

Note that if we draw a line segment connecting the centers of the circles, we get the length of this segment equals to triple the diameter of one circle.

The area of the five circles is $20\pi$ , thus the area of one circle is $4\pi =\pi\times r^2\implies r^2=4\implies d=4$ .

The measure of the side of the square is $4\times 3=12 \implies s^2=144$ which is the area of the square.