It is known that one side of the rectangle ABCD is AB=4cm, and the other side BC=2cm. If it is rotated around the straight line AB for one revolution, what is the surface area of the cylinder obtained?
已知长方形ABCD的一边AB=4cm，另一边BC=2cm，以直线AB为轴旋转一周，所得到的圆柱的表面积是多少．
<gadget id="calculator">2 * 3.14 * 2 * 4</gadget>
<output>50.24</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4 * 2</gadget>
<output>25.12</output>

<gadget id="calculator">50.24 + 25.12</gadget>
<output>75.36</output>

<result>75.36</result>