13. As shown in the figure, $ABCD$ is a square. Two ants $\mathbf{P}$ and $\mathbf{Q}$ start from point $\mathbf{C}$ at the same time, both moving at a speed of $0.25 CD /$ second. $\mathbf{P}$ moves along the ray $CD$ (the ray means that after the ant reaches point $\mathbf{D}$, it continues to move in the $CD$ direction), and $\mathbf{Q}$ moves along the ray $CB$. After moving for 2 seconds, the area of the overlapping part of $\triangle QPC$ and square $ABCD$ is 100 square centimeters. Then, after moving for $\mathbf{5}$ seconds, what is the area of the overlapping part of $\triangle QPC$ and square $ABCD$?
【Analysis】Geometry, Cut and Fill Method;
After the first 2 seconds, $\mathrm{P}$ and $\mathrm{Q}$ are at the midpoints of $\mathrm{CD}$ and $\mathrm{BC}$, respectively, so $S_{A B C D}=100 \times 8=800\left(\mathrm{~cm}^{2}\right)$;

After the second 5 seconds, as shown in the figure, using the cut and fill method, we can get $S_{\text {inside }}=800 \div(16 \times 2) \times 23=575\left(\mathrm{~cm}^{2}\right)$.