Dad reads a book, and insists on reading 25 pages every day. From January 29th, he just finished the book on February 17th. How many pages does this book have?
爸爸看一本书，每天坚持看25页，从一月29日开始看到二月17日刚好把这本书看完，这本书有多少页？
<gadget id="calculator">25 * 20</gadget>
<output>500</output>

<result>500</result>