let's find the area by parts
red is the first part
we need the area of the red square an substract the mid-circle area
square is A=bxh
so A=2x4=8
the area of the circle is A=pi x r2
so the area of the circle is A=pi x 4 and the middle is 2pi
the total red area is
green part
te area is A=bxh, the heigth is 4 like the diameter of the circle and the base is 8 less 2 (of the radius) and less 4(of the base