piece of cardboard is square, with a side length of 30 cm. Cut off a small square with a side length of 5 cm from the four corners, and then make a box without a lid. What is the volume of this box?
一张硬纸板是正方形的，边长是30cm，从四个角上分别剪掉边长是5cm的小正方形，然后做成无盖的盒子，这个盒子的容积是多少？
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">30 - 10</gadget>
<output>20</output>

<gadget id="calculator">20 * 20 * 5</gadget>
<output>2_000</output>

<result>2_000</result>