There is a rectangular iron sheet with a length of 40 cm and a width of 30 cm. After cutting off squares of equal area on the four corners, an iron box with a depth of 6 cm is just made. Find the volume of this iron box?
有一个长40厘米、宽30厘米的长方形的铁皮，在4个角上分别剪去面积相等的正方形后，正好制成一个深6厘米的铁盒，求这个铁盒的容积？
<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">40 - 12</gadget>
<output>28</output>

<gadget id="calculator">30 - 12</gadget>
<output>18</output>

<gadget id="calculator">6 / 1_000</gadget>
<output>3/500 = around 0.006</output>

<gadget id="calculator">28 * 18 * (3/500)</gadget>
<output>378/125 = around 3.024</output>

<result>378/125 = around 3.024</result>