After a square log with a length of 5.2dm is sawn into two identical pieces of square logs, the surface area increases by 4dm**2. What is the original volume of this square log?
长是5.2dm的方木被锯成相同的两段方木后，表面积增加了4dm**2，原来这根方木的体积是多少？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 * 5.2</gadget>
<output>10.4</output>

<result>10.4</result>