If a cylinder with a diameter of 4 cm and a height of 5 cm is cut into two half cylinders along the diameter of the bottom, how much is the surface area increased in square centimeters?
把一个直径为4厘米，高为5厘米的圆柱，沿底面直径切割成两个半圆柱，表面积增加了多少平方厘米．
<gadget id="calculator">5 * 4 * 2</gadget>
<output>40</output>

<result>40</result>