Re-entry. What will happend?

[erikstudent]

I've been in USA for almost 3 months. Can stay til july 5. according to my I-94.
Leaving U.S for a study-trip to china. But I'll return june 13.
But I'm interested to stay an extra 6 months when I return. For deeper studing in my school. So:

1. How long can I stay after re-entering? (what will my new I-94 say)
2. Do I need to apply for an extension of my current visa, before I leave on my trip?

Thanks. Hope you understand my situation. =)