Cut out the largest circle from a rectangular cardboard with a length of 10 cm and a width of 8 cm. What is the remaining area of the cardboard?
从一张长10厘米，宽8厘米的长方形纸板上剪去一个最大的圆，纸板剩下的面积是多少．
<gadget id="calculator">10 * 8</gadget>
<output>80</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

<gadget id="calculator">80 - 50.24</gadget>
<output>29.76</output>

<result>29.76</result>