What is the area in square centimeters of the largest circle cut out of a rectangular cardboard with a length of 5 cm and a width of 4 cm?
在一个长5厘米，宽4厘米的长方形硬纸上剪下一个最大的圆剪去部分的面积是多少平方厘米．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

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

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

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">20 - 12.56</gadget>
<output>7.44</output>

<result>7.44</result>