The school library bought a batch of new books. The price of "Encyclopedia of Knowledge" is 19.80 yuan, and the price of "Fairy Tales" is 16.20 yuan. The two kinds of books are 25 books each. How much is the total cost?
学校图书馆买来一批新书，《百科知识》定价是19.80元，《童话故事》定价是16.20元，两种书各买25本，一共用了多少钱？
<gadget id="calculator">19.8 + 16.2</gadget>
<output>36</output>

<gadget id="calculator">36 * 25</gadget>
<output>900</output>

<result>900</result>