cube water tank with a side length of 12 decimeters is filled with half a tank of water. When the first cuboid iron block is put in, the water level rises by 2.5 decimeters, and when the second cuboid iron block is put in, the water level rises 4 decimeters (the iron blocks put in twice are completely submerged in water), how many cubic decimeters is the volume difference between the two iron blocks?
一个棱长是12分米的正方体水缸，里面装了半缸水，当放进第一个长方体铁块后，水面上升了2.5分米，当放进第二个长方体铁块后，水面上升了4分米(两次放入的铁块都完全浸入水中)，则这两个铁块的体积相差多少立方分米？
<gadget id="calculator">4 - 2.5</gadget>
<output>1.5</output>

<gadget id="calculator">12 * 12 * 1.5</gadget>
<output>216</output>

<result>216</result>