There are two circles, big and small. The circumference of the small circle is 12.56 meters. The diameter of the big circle is twice the diameter of the small circle. What is the area of the big circle?
有大、小两个圆，小圆周长是12.56米，大圆直径是小圆直径的2倍，大圆的面积是多少．
<gadget id="calculator">12.56 / 3.14</gadget>
<output>4</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>