A rectangular cardboard with a length of 28 cm and a width of 18 cm is cut from the four corners to a square with a side length of 6 cm, and then folded into a box. How much cardboard is used for this box?
一张长28厘米，宽18厘米的长方形硬纸板，从四个角剪去边长6厘米的正方形，然后折成一个盒子．这个盒子用了多少纸板？
<gadget id="calculator">28 * 18</gadget>
<output>504</output>

<gadget id="calculator">6 * 6 * 4</gadget>
<output>144</output>

<gadget id="calculator">504 - 144</gadget>
<output>360</output>

<result>360</result>