~*How much should I charge for tutoring*~?

Ok, I'm raising money for the Summer and well, the school ped off tutoring papers to some kids (for TAKS) and my friend's mom wanted me to tutor her instead of the teachers tutoring her on Saturday mornings. So,yep. I'm trying not to give an expensive price because of so many things. How much should I charge her (mom/dad) for tutoring? Thx 4 Answerin'!