Beijing Jiuzhang Bookstore implements a preferential measure for customers: a 5% discount for each purchase of books ranging from 200 yuan to 499.99 yuan, and a 10% discount for each purchase of more than 500 yuan (including 500 yuan). A customer bought three books in a bookstore. If the first and second purchases are combined, it is 13.5 yuan cheaper than buying them separately; if the three purchases are combined together, it is 39.4 yuan cheaper than the three separate purchases. Knowing that the price of the first book is the price of the third book (5/8), ask the customer how much he bought the book for the second time.
北京九章书店对顾客实行一项优惠措施：每次买书200元至499.99元者优惠5%，每次买500元以上者(包含500元)优惠10%．某顾客到书店买了三次书，如果第一次与第二次合并一起买，比分开买便宜13.5元；如果三次合并一起买比三次分开买便宜39.4元．已经知道第一次的书价是第三次书价的(5/8)，问这位顾客第二次买了多少钱的书．
<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">13.5 / (1/20)</gadget>
<output>270</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">270 * (1/10)</gadget>
<output>27</output>

<gadget id="calculator">39.4 - 27</gadget>
<output>12.4</output>

<gadget id="calculator">(1/10) - (1/20)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">12.4 / (1/20)</gadget>
<output>248</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">248 * (5/8)</gadget>
<output>155</output>

<gadget id="calculator">270 - 155</gadget>
<output>115</output>

<result>115</result>