Build a cylindrical biogas digester with a bottom diameter of 4 meters and a depth of 2 meters. Put cement on the four walls and bottom of the pool, how many square meters is the area of the cement part?
修建一个圆柱形的沼气池，底面直径是4米，深2米．在池的四壁与底面抹上水泥，抹水泥部分的面积是多少平方米？
<gadget id="calculator">3.14 * 4 * 2</gadget>
<output>25.12</output>

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

<gadget id="calculator">25.12 + 12.56</gadget>
<output>37.68</output>

<result>37.68</result>