如何编写一个xQuery来提取两个基于条件的其他值的字段？

<books>
  <book>
    <title>Book 1</title>
    <author>Author 1</author>
    <price>10</price>
  </book>
  <book>
    <title>Book 2</title>
    <author>Author 2</author>
    <price>20</price>
  </book>
  <book>
    <title>Book 3</title>
    <author>Author 3</author>
    <price>30</price>
  </book>
</books>

for $book in /books/book
where $book/price > 20
return <result>
         <title>{data($book/title)}</title>
         <author>{data($book/author)}</author>
       </result>

<result>
  <title>Book 2</title>
  <author>Author 2</author>
</result>
<result>
  <title>Book 3</title>
  <author>Author 3</author>
</result>