A semicircular lawn has a perimeter of 308.4m, what is its area in square meters?
一个半圆形草坪，它的周长是308.4m，它的面积是多少平方米？
<gadget id="calculator">120 / 2</gadget>
<output>60</output>

<gadget id="calculator">60 ** 2</gadget>
<output>3_600</output>

<gadget id="calculator">3_600 / 2</gadget>
<output>1_800</output>

<gadget id="calculator">3.14 * 1_800</gadget>
<output>5_652</output>

<result>5_652</result>