20. The left figure is an open-top rectangular box, with a height of $30 \mathrm{~cm}$ and a base that is a square with side length $80 \mathrm{~cm}$. After cutting this box open, the right figure is obtained. From the right figure, cut out the largest possible square. The area of this square is $\qquad$ $\mathrm{cm}^{2}$
$11200$