If the perimeter of a square is 8.4 meters, what is its area in square meters?
一个正方形的周长是8.4米，它的面积是多少平方米．
<gadget id="calculator">8.4 / 4</gadget>
<output>2.1</output>

<gadget id="calculator">2.1 * 2.1</gadget>
<output>4.41</output>

<result>4.41</result>