A barrel of oil weighs 5.8 kilograms, and after half of the oil is sold, the weight of the barrel is 3.3 kilograms. If the price per kilogram of oil is 4.2 yuan, how much can you get for selling all these oils?
一桶油连桶重5.8千克，卖出油的一半后，连桶重3.3千克．如果每千克油的价格是4.2元，那么这些油全部卖出可得多少钱？
<gadget id="calculator">5.8 - 3.3</gadget>
<output>2.5</output>

<gadget id="calculator">2.5 * 2</gadget>
<output>5</output>

<gadget id="calculator">5 * 4.2</gadget>
<output>21</output>

<result>21</result>