A7. The side of the square is $6 \mathrm{~cm}$ long. In each corner of the square, we draw a circle with a radius of $3 \mathrm{~cm}$ (see figure). The area of the shaded figure is $x$. $(4-\pi) \mathrm{cm}^{2}$. The value of $x$ is:
(A) 3
(B) 6
(C) 9
(D) 36
(E) 40
A7. The area of the shaded figure represents the difference between the area of a square with side length $a=6 \mathrm{~cm}$ and the area of a circle with radius length $r=3 \mathrm{~cm}$, and is given by $S=a^{2}-\pi r^{2}=$ $36-\pi \cdot 9=9 \cdot(4-\pi) \mathrm{cm}^{2}$. The factor $x=9$.