It depends on your genetics and how well you eat, if you eat more and have some chub then your more likely to get bigger breasts because they are mainly fat cells and other stuff.
Well, it depends on how far into puberty you are. Some 11 yr olds have a completely flat chest while others seem huge. My secret is wear the bras you find in the kids underwear section to school...
This is not something that you have to have people on the Internet solve for you. It's very easy:
There is no perfect bra size for an 11 year old. It varies with everyone. You might have twin...