There are 9 identical bookcases in the school library, and each bookcase has 4 floors, with an average of 250 books on each floor. How many books are there in the school library?
学校图书室有9个同样的书柜，每个书柜有4层，平均每层放250本书．学校图书室一共摆放了多少本书？
<gadget id="calculator">250 * 4 * 9</gadget>
<output>9_000</output>

<result>9_000</result>