A cuboid fish tank is 2.5 meters long, 0.8 meters wide, and the water depth inside is 5 decimeters. After putting some ornamental stones into the fish tank, the water depth is 7 decimeters. What is the volume of these stones?
一个长方体鱼缸长2.5米，宽0.8米，里面的水深5分米，把一些观赏石头放入这个鱼缸后，这时的水深7分米，这些石头的体积是多少立方分米？
<gadget id="calculator">2.5 * 10</gadget>
<output>25</output>

<gadget id="calculator">0.8 * 10</gadget>
<output>8</output>

<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">25 * 8 * 2</gadget>
<output>400</output>

<result>400</result>