Cut off the largest circle from a rectangle with a length of 5 cm and a width of 4 cm, what is the area of the remaining part in square centimeters?
在一个长5厘米，宽4厘米的长方形里剪去一个最大的圆，剩下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>