To make a glass fish tank with a length of 6 meters, a width of 4 meters and a height of 2 meters without a cover, at least how much glass is needed.
要做一个长是6米，宽是4米，高是2米的无盖的玻璃鱼缸，至少需要玻璃多少．
<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">40 + 24</gadget>
<output>64</output>

<result>64</result>