A library has 20 identical bookshelves, each shelf has 5 layers, and each layer holds 135 books. How many books can these bookshelves hold in total?
一个图书馆有20个同样的书架，每个书架有5层，每层放135本书．这些书架一共能放多少本书？
<gadget id="calculator">135 * 5 * 20</gadget>
<output>13_500</output>

<result>13_500</result>