How much should I charge for knitting instruction?

I taught a knitting class in my homeschool co-op a few years ago. I really enjoyed teaching, and I'd love to get back in the game!

I'm thinking about applying at my local public library to teach an ongoing class, as well as posting classes and private lessons on Craigslist. I am only seventeen but I'm a highly experienced crafter, and I am confident that I can tackle any knitting situation that comes my way. I'm no rookie; my lessons would be worthwhile.

What should I charge for my time, in private lessons and in classes held by myself or through the public library and other venues?

Thanks! :)