Yeah I think around $25-$35 is the pretty standard rate for someone coming right out of high-school. I'd think with your qualifications though it wouldn't be ridiculous to charge for more. I read somewhere on the forums that qualified teachers for the relevant subject could start at $50 and onward. In terms of what to expect, that's hard to answer. No one could begrudge you asking for a higher than standard price however, whether or not people would actually pay that is a different story. $40 seems legit I guess (no basis for this, just sounds alright).
-separate thought- depends on groups as well, I guess - I know Thushan tutors for about $30 an hour, which is pretty standard, however I think that's from every person within a group of five for the same hour. And I guess that's pretty cool 'cause Thushan's a monster and it's a solid price in terms of what it usually is, just in a group.