If the radius of the circle is increased from 3 cm to 4 cm, how much does the area of the circle increase in square centimeters?
圆的半径由3厘米增加到4厘米，圆的面积增加多少平方厘米
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

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

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

<gadget id="calculator">50.24 - 28.26</gadget>
<output>21.98</output>

<result>21.98</result>