A cylindrical oil barrel was originally 8 decimeters high, but now it needs to be increased by 5 decimeters, so that the surface area increases by 6.28 square decimeters. What is the current volume of the oil barrel in cubic decimeters?
一个圆柱形油桶，原来高8分米，现在需要加高5分米，这样表面积增加6.28平方分米，油桶现在的容积是多少立方分米？
<gadget id="calculator">6.28 / 5</gadget>
<output>1.256</output>

<gadget id="calculator">1.256 / 3.14 / 2</gadget>
<output>0.2</output>

<gadget id="calculator">0.2 ** 2</gadget>
<output>0.04</output>

<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">3.14 * 0.04 * 13</gadget>
<output>1.6328</output>

<result>1.6328</result>