Xiaoli bought a copy of "Story King" for 13.20 yuan, and another copy of "Fun Math" for 26.70 yuan. Which book is more expensive? How much is it expensive?
小丽买了一本《故事大王》花了13.20元，又买了一本《趣味数学》花了26.70元，哪本书贵？贵多少元？
<gadget id="calculator">26.7 - 13.2</gadget>
<output>13.5</output>

<result>13.5</result>