A cone-shaped copper billet has a volume of 7 cubic decimeters. Cut off the upper cone from one-third of its height, and put the remaining part in a cylindrical box. What is the minimum volume of this box? cubic decimeter.
一根圆锥体铜坯，体积是7立方分米，把它从高的三分之一处截去上面的小圆锥，剩下的部分装在一个圆柱形盒中，这个盒子的容积最小是多少立方分米．
<gadget id="calculator">3 / 1</gadget>
<output>3</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(2/3) * 21</gadget>
<output>14</output>

<result>14</result>