cuboid glass fish tank is 5 decimeters long and 2 decimeters wide. The water depth is 2.5 decimeters after an irregular stone is put in, and the water level drops 0.8 decimeters after the stone is removed. What is the volume of this stone.
有一长方体的玻璃鱼缸，长是5分米，宽是2分米．放入一块不规则的石头后水深2.5分米，捞出这块石头后，水面下降0.8分米．这块石头的体积是多少．
<gadget id="calculator">5 * 2 * 0.8</gadget>
<output>8</output>

<result>8</result>