A rectangular parallelepiped steel with a length of 3 meters is cut into two sections along the cross section, and the surface area increases by 4.2 square decimeters. What is the original volume of the rectangular parallelepiped steel?
一根长3米的长方体钢材，沿横截面截成两段后，表面积增加4.2平方分米，这根长方体钢材原来的体积是多少立方分米．
<gadget id="calculator">4.2 / 2</gadget>
<output>2.1</output>

<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">2.1 * 30</gadget>
<output>63</output>

<result>63</result>