Cut out the largest circle from a rectangle with a length of 7 decimeters and a width of 4 decimeters. What is the area of the circle in square meters?
从一张长7分米，宽4分米的长方形上，剪下一个最大的圆，圆的面积是多少平方米？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>