copy of "The King of Stories" is priced at 13.6 yuan, and a copy of "Stories of Idioms" is priced at 10.8 yuan.
一本《故事大王》定价13.6元，一本《成语故事》定价10.8元，一本《大事大王比一本《成语故事》贵多少钱？
<gadget id="calculator">13.6 - 10.8</gadget>
<output>2.8</output>

<result>2.8</result>