What's the going rate for CMA AP tutor?

I completed AP last year with 90+ and CMA emailed me asking if I want to be a tutor, thought it's volunteer and replied "yes", but later received email saying "rate will be decided by your own", so it seems I'll get paid. Then I got email from AP students asking rate, but I have no clue at all.

Anyone by chance being a tutor or hired one before? So what's the rate? Or what's normally rate for similar ones?

I don't really care if I make couple $ more, but doesn't want sound "Cheap" by giving a very low rate.

Thanks for your input.