If the area of a rectangle is 20 square meters and its length and width are doubled, what is the area in square meters?
一个长方形的面积是20平方米，长和宽都扩大2倍，面积是多少平方米．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>