A bottle of drink is 4.7 yuan, which is 0.5 yuan more expensive than a bottle of black tea. The money for two bottles of black tea just buys a barrel of orange juice. How much is a barrel of orange juice?
一瓶饮料4.7元，比一瓶红茶贵0.5元，两瓶红茶的钱正好买一桶橘子汁，一桶橘子汁多少元？
<gadget id="calculator">4.7 - 0.5</gadget>
<output>4.2</output>

<gadget id="calculator">4.2 * 2</gadget>
<output>8.4</output>

<result>8.4</result>