One square meter of green grass can release 15g of oxygen a day. According to this calculation, how many grams of oxygen can be released a day for a circular grass with a circumference of 18.84 meters?
一平方米的绿草一天能够释放15g氧气，照这样计算，一块周长是18.84米的圆形草地，一天可以释放多少克氧气？
<gadget id="calculator">2 * 3.14</gadget>
<output>6.28</output>

<gadget id="calculator">18.84 / 6.28</gadget>
<output>3</output>

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

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

<gadget id="calculator">28.26 * 15</gadget>
<output>423.9</output>

<result>423.9</result>