It's already out.
Rangers Apprentice 11 will come out in 2011 October
It is already out.
October 12 2010
Oct 4th 2011
It will come out on June 15, 2010
Book 6 has already come out.
no book 10, 11, and 12 are yet to come out
Now
2011
I don't know, but you can buy the Australian version of it on Amazon.
It should be ten at the moment although the tenth book hasn't come out in some countries yet.