To make a rectangular washing machine packing box, it is 60 cm long, 40 cm wide, and 80 cm high. How much cardboard should be used at least?
做一个长方体的洗衣机包装箱，它长60厘米，宽40厘米，高80厘米，至少要用多少硬纸板？
<gadget id="calculator">60 * 40</gadget>
<output>2_400</output>

<gadget id="calculator">60 * 80</gadget>
<output>4_800</output>

<gadget id="calculator">40 * 80</gadget>
<output>3_200</output>

<gadget id="calculator">2_400 + 4_800 + 3_200</gadget>
<output>10_400</output>

<gadget id="calculator">10_400 * 2</gadget>
<output>20_800</output>

<result>20_800</result>