G2.4 In the coordinate plane, the area of the region bounded by the following lines is $D$ square units, find the value of $D$.
$$
\begin{array}{l}
L_{1}: y-2=0 \\
L_{2}: y+2=0 \\
L_{3}: 4 x+7 y-10=0 \\
L_{4}: 4 x+7 y+20=0
\end{array}
$$

It is easy to show that the bounded region is a parallelogram $A B C D$ with vertices $A(-1.5,-2)$, $B(6,-2), C(-1,2), C(-8.5,2)$.
The area $D=|6-(-1.5)| \times|2-(-2)|=7.5 \times 4=30$