Build a cylindrical water tower with an internal bottom diameter of 4 meters and a height of 5 meters. What is the area in square meters that needs to be plastered with cement?
建造一个圆柱形水塔，内部底面直径是4米，高是5米，里面需抹水泥的面积是多少平方米．
<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>

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

<gadget id="calculator">12.56 + 62.8</gadget>
<output>75.36</output>

<result>75.36</result>