A trapezoidal iron sheet has an upper base of 8 decimeters, a lower base of 4 decimeters, and a height of 10 decimeters. If the price of iron sheets per square decimeter is 5 yuan, how much should you pay if you buy such iron sheets for 50 yuan?
一块梯形铁皮，上底是8分米，下底是4分米，高是10分米．如果每平方分米的铁皮的售价是5元，买这样的铁皮50块，应付多少元？
<gadget id="calculator">8 + 4</gadget>
<output>12</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">12 * 5 * 5 * 50</gadget>
<output>15_000</output>

<result>15_000</result>