A square with a side length of 4.71 meters is exactly surrounded by a piece of iron wire. If this wire is used to form a circle, what is the area of the circle? (not counting joints)
用一根铁丝刚好围成一个边长是4.71米的正方形．如果用这根铁丝改围成圆形，这个圆形的面积有多大？(接头处不计)
<gadget id="calculator">4.71 * 4</gadget>
<output>18.84</output>

<gadget id="calculator">18.84 / 3.14 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<result>28.26</result>