Two good friends went to a bookstore to buy an interesting book. After reading the price of the book, they found that the money one brought was still short of 2 yuan and 50 cents, and the other was short of 3 yuan and 10 cents. Putting the money of the two together is 8 yuan and 4 cents. If two people buy this book together, is the money more than enough or not enough? How much is the difference?
两位好朋友到书店买一本有趣的书，看了书的定价后发现，一位所带的钱还缺2元5角，另一位缺3元1角．把两人的钱合起来是8元4角．如果两人合买这本书，钱是有余还是不够？相差多少钱？
<gadget id="calculator">2.5 + 3.1</gadget>
<output>5.6</output>

<gadget id="calculator">8.4 + 5.6</gadget>
<output>14</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<gadget id="calculator">8.4 - 7</gadget>
<output>1.4</output>

<result>1.4</result>