Wang Ming wants to make 20 cuboid cardboard boxes, each with a length of 12cm, a width of 6cm, and a height of 3cm. How many square centimeters of cardboard does he need to prepare?
王明要做20个长方体硬纸盒，每个纸盒的长是12cm，宽是6cm，高是3cm，他需要准备多少平方厘米硬纸板？
<gadget id="calculator">12 * 6</gadget>
<output>72</output>

<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<gadget id="calculator">3 * 12</gadget>
<output>36</output>

<gadget id="calculator">72 + 18 + 36</gadget>
<output>126</output>

<gadget id="calculator">126 * 2 * 20</gadget>
<output>5_040</output>

<result>5_040</result>