library has 20 bookshelves, each shelf has 5 layers, and each layer contains 60 books. How many books are there in total in this library?
一个图书室有20个书架，每个书架放5层，每层放60本书，这个图书室共放书多少本？
<gadget id="calculator">60 * 5 * 20</gadget>
<output>6_000</output>

<result>6_000</result>