A trapezoidal billboard has an upper base of 13 meters, a lower base of 18 meters, and a height of 4 meters. To paint the two sides of this billboard with paint, 1.2kg of paint is needed per square meter, how many kg of paint is needed in total?
一块梯形的广告牌，它的上底是13米，下底是18米，高是4米．用油漆涂刷这块广告牌的两面，每平方米需要油漆1.2kg，一共需要多少kg油漆？
<gadget id="calculator">13 + 18</gadget>
<output>31</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">31 * 2 * 1.2</gadget>
<output>74.4</output>

<result>74.4</result>