cow is tied to a stake in a meadow with a rope length of 4 meters. What is the maximum area in square meters that the cow can eat grass?
草地的木桩上拴着一头牛，绳长4米，这头牛能够吃到草的最大面积是多少平方米？
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>