All 4 bases have the 145. If you want MIA, you need to bid the 145. Mia officially opens Sept. 1, so it's hard to say how senior/junior it will be, but I would find it hard to believe it would take you more than a few months to get it if you don't get it in class. Just bid the 145 and you're in good shape. You should be able to get the 145 no matter how young you are.