A cuboid sewer pipe with a length of 4 meters is a rectangle with a length of 15 cm and a width of 10 cm. How much material is needed to make this sewer pipe at least.
一个长4米长方体下水管，下水口是长15厘米，宽10厘米的长方形．做这个下水管至少需要多少材料．
<gadget id="calculator">4 * 100</gadget>
<output>400</output>

<gadget id="calculator">400 * 15</gadget>
<output>6_000</output>

<gadget id="calculator">400 * 10</gadget>
<output>4_000</output>

<gadget id="calculator">6_000 + 4_000</gadget>
<output>10_000</output>

<gadget id="calculator">10_000 * 2</gadget>
<output>20_000</output>

<result>20_000</result>