A fish tank filled with water has a length of 30 cm and a width of 20 cm. The water surface is 6cm high before a stone is completely submerged, and rises to 10cm after immersion. What is the volume of the stone in the glass fish tank?
一个盛有水的鱼缸，长是30cm，宽是20cm．水面在完全浸没一块石头前是6cm高，浸没后升高至10cm，请问玻璃鱼缸中的石头体积是多少？
<gadget id="calculator">10 - 6</gadget>
<output>4</output>

<gadget id="calculator">30 * 20 * 4</gadget>
<output>2_400</output>

<result>2_400</result>