A teacup with a round bottom, the circumference of the bottom circle is 18.84 cm, what is the area of the bottom in square centimeters?
一个底面是圆形的茶杯，底面圆的周长是18.84厘米，底面积是多少平方厘米．
<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>