There are two circles, A and B, and the circumference of circle A is increased by 10 centimeters after cutting circle A into an approximate rectangle. The area of circle B is 1/5 less than that of circle A. What is the area of circle B in square centimeters?
有A、B两个圆，将A圆割拼成近似的长方形后周长增加了10厘米，B圆的面积比A圆少(1/5)，则B圆的面积是多少平方厘米．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">3.14 * 25 * (4/5)</gadget>
<output>62.8</output>

<result>62.8</result>