[XHTML 2] Section 5.5 quality values.

Dear HTML Working Group,

In Section 5.5 ContentTypes, it is not clear what the user agent should do 
in this situation

<p src="logo" type="image/png; q=0.5, image/jpeg;q=0.1">

with a user agent values of

image/png;q=0.1, image/jpeg;q=0.9;

Please clarify the section to explain how  document quality values, and user 
agent quality values combine.

Regards,

Jim Ley.