A cuboid fish tank without a cover is 45 cm long, 40 cm wide, and 30 cm high. How much glass is needed to make such a fish tank?
一个无盖的长方体鱼缸，长45厘米，宽40厘米，高30厘米，做一个这样的鱼缸需要多少玻璃？
<gadget id="calculator">45 * 40</gadget>
<output>1_800</output>

<gadget id="calculator">45 * 30 * 2</gadget>
<output>2_700</output>

<gadget id="calculator">40 * 30 * 2</gadget>
<output>2_400</output>

<gadget id="calculator">1_800 + 2_700 + 2_400</gadget>
<output>6_900</output>

<result>6_900</result>