G2.1 In Figure 1, two rectangles with widths 4 and 5 units cross each other at $30^{\circ}$. Find the area of the overlapped region.
$\begin{array}{l}\text { Let } A B=x, B C=y, \angle A B C=30^{\circ} \\ x \sin 30^{\circ}=5 \Rightarrow x=10 \\ y \sin 30^{\circ}=4 \Rightarrow y=8 \\ \text { Area }=x y \sin 30^{\circ}=10 \times 8 \times 0.5=40\end{array}$