reservoir is 40m long, 20m wide and 4m deep. Its walls and bottom are inlaid with ceramic tiles. What is the area of inlaid tiles?
一个蓄水池长40m，宽20m，深4m．它的四壁及底面都镶上瓷砖，镶瓷砖的面积是多少？
<gadget id="calculator">40 * 20</gadget>
<output>800</output>

<gadget id="calculator">20 * 4 * 2</gadget>
<output>160</output>

<gadget id="calculator">40 * 4 * 2</gadget>
<output>320</output>

<gadget id="calculator">800 + 160 + 320</gadget>
<output>1_280</output>

<result>1_280</result>