Get book nodes where node and parent node contains an attribute

Please provide xpath expresion for the problem below:
 
From the sample xml shown in the link below.
http://stackoverflow.com/questions/1457638/xpath-get-nodes-where-child-node-contains-an-attribute

The required xpath expression is : all book titles whose language="en" (English attribute in node)  and category="WEB" (parent)

Solution should look like:
 //book/title[@lang='en' and <your expression goes here>]

The expected result is:
  <title lang="en">XQuery Kick Start</title>
  <title lang="en">Learning XML</title>

Thank you