A barrel of oil weighs 54.4 kilograms, and after half of the oil is sold, the weight of the barrel is 28.6 kilograms. How many kilograms does the barrel weigh?
一桶油连桶重54.4千克，卖出一半油后，连桶还重28.6千克．桶重多少千克？
<gadget id="calculator">54.4 - 28.6</gadget>
<output>25.8</output>

<gadget id="calculator">25.8 * 2</gadget>
<output>51.6</output>

<gadget id="calculator">54.4 - 51.6</gadget>
<output>2.8</output>

<result>2.8</result>