Jingjing and Beibei both wanted to buy the same book in the bookstore, but Jingjing was short of 2.2 yuan and Beibei was short of 1.5 yuan. In the end, the two bought this book together, and they had a total of 2.3 yuan left. How much is this book?
京京和贝贝在书店里都想买同一本书，但京京缺2.2元，贝贝缺1.5元．最后两人合买了这本书，他们共剩余2.3元，这本书多少元．
<gadget id="calculator">2.2 + 1.5 + 2.3</gadget>
<output>6</output>

<result>6</result>