Teacher Wang wants to buy 24 books of "Chinese Stories" for our class. Guangming Bookstore sells each book at a discount of 10% of the original price; Qiuzhi Bookstore buys 5 books for free, and dissatisfied will not give away. The price of each copy of "China Stories" in these two bookstores is 10 yuan. Please do the math: Which bookstore is the cheapest for Mr. Wang to buy? How much is the minimum cost?
王老师要为我们班购买24本《中国故事》书，光明书店每本按原价优惠10%出售；求知书店每买5本送一本，不满不送．这两个书店的《中国故事》每本标价都是10元，请你算一算：王老师到哪一家书店购买比较便宜？最少要花多少钱？
<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<gadget id="calculator">24 / 6</gadget>
<output>4</output>

<gadget id="calculator">24 - 4</gadget>
<output>20</output>

<gadget id="calculator">20 * 10</gadget>
<output>200</output>

<result>200</result>