I've heard that doing extension 2 mathematics will cause extension 1 to count as 2 units, and extension 2 to count as another 2 units, and you wouldn't do a 2U advanced exam. So if I've done accelerated 2U advanced and done well in the HSC for it, and am planning on doing extension 2 for year 12, will my 2U advanced mark mean anything to my ATAR since I've actually done and exam, as opposed to those who learnt the content but didn't sit an exam?