My timetable is 5 hours. This is then split between two teachers and, of course there is more extra reading and question doing etc. outside of lessons, I feel you should try to tell yourself that this takes another 2 hours (yes, I'm a really lazy guy and don't even do that, but many/most do, ...except maybe at exam time!) Thus, we are at 7 hours a week.
Clearly there is no amount you need to do in orderto get an A. I would say I don't do much work, but I do work hard...a fine distinction. Putting aside 7 hours a week isn't going to get you an A, but working really hard for 7 hours a week, I feel, should/could.
I haven't factored in the whole self-teaching thing here: perhaps you might want to add a little which you can spend throwing balls around in your garden to investigate the independance of horizontal and vertical motion, or calculating the specific heat capacity of your dinner in the microwave.