Build a barrage 2.5 kilometers long, its cross-section is a trapezoid with an upper base of 6 meters, a lower base of 14 meters and a height of 7.8 meters. How many cubic meters of earth and rock will be used to build this barrage?
筑一段长2.5千米的拦河坝，它的横截面是一个上底6米、下底14米、高7.8米的梯形．筑这段拦河坝要用土石多少立方米？
<gadget id="calculator">14 + 6</gadget>
<output>20</output>

<gadget id="calculator">7.8 / 2</gadget>
<output>3.9</output>

<gadget id="calculator">2.5 * 1_000</gadget>
<output>2_500</output>

<gadget id="calculator">20 * 3.9 * 2_500</gadget>
<output>195_000</output>

<result>195_000</result>