Paint the front and back sides of a trapezoidal billboard, the upper base is 4 meters, the lower base is 5 meters, and the height is half of the upper base. If 0.6 kg of paint is used per square meter, how many kg of paint is needed?
刷梯形广告牌的正反两面，上底4米，下底5米，高是上底的一半，如果每平方米用油漆0.6千克，需要多少千克油漆？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

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

<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">9 * 1 * 2</gadget>
<output>18</output>

<gadget id="calculator">18 * 0.6</gadget>
<output>10.8</output>

<result>10.8</result>