The casting factory originally had an iron chimney with a cross-sectional diameter of 0.84 meters and a height of 15 meters. Now it is necessary to increase the height of the chimney to 25 meters. How many square meters of iron sheet is needed at least? (Joints are not counted)
铸件厂原有一个铁皮烟囱，横截面的直径是0.84米，高是15米，现要将烟囱加高到25米，问至少还需要铁皮多少平方米？(接头处不计算)
<gadget id="calculator">25 - 15</gadget>
<output>10</output>

<gadget id="calculator">3.14 * 0.84 * 10</gadget>
<output>26.376</output>

<result>26.376</result>