A ring has an outer radius of 2 decimeters and an inner circumference of 6.28 decimeters. What is its area in square decimeters?
一个圆环，外圆半径是2分米，内圆周长是6.28分米，它的面积是多少平方分米？
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">6.28 / 3.14 / 2</gadget>
<output>1</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3.14 * 3</gadget>
<output>9.42</output>

<result>9.42</result>