Cut a largest circle on a rectangular iron plate with a length of 6 decimeters and a width of 4 decimeters. What is the area of this circle?
在长6分米，宽4分米的长方形铁片上剪一个最大的圆，这个圆的面积是多少．
<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>