Lan Lan uses a piece of rectangular paper with a length of 5 cm and a width of 4 cm to cut out the largest circular school utensil. What is the area of this round school utensil in square centimeters?
兰兰用一张长5厘米、宽4厘米的长方形纸，剪一个最大的圆形学具，则这个圆形学具的面积是多少平方厘米．
<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>

<result>12.56</result>