4. (8 points) 3 identical square pieces of paper are stacked in the same direction (as shown in the figure), with vertices $A$ and $B$ coinciding with the center points of the squares. If the perimeter of the resulting shape is 48 cm, then the area covered by this shape is square centimeters.
【Solution】Solution: $48 \div 2 \div 4=6$ (cm)
$$
\begin{array}{l}
6 \div 2=3 \text { (cm) } \\
6 \times 6 \times 2+3 \times 3 \times 2 \\
=72+18 \\
=90 \text { (square cm) }
\end{array}
$$

Answer: The area covered by this shape is 90 square cm. Therefore, the answer is: 90.