circular water tank with a cylinder mouth circumference of 25.12 decimeters, to make a cylinder head for this water tank, what is the minimum area of the cylinder head?
一个缸口周长是25.12分米的圆形水缸，要给这个水缸做一个缸盖，这个缸盖至少要多大面积？
<gadget id="calculator">2 * 3.14</gadget>
<output>6.28</output>

<gadget id="calculator">25.12 / 6.28</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>