"Yeah sure, how about today after school?"

"Thank you so much John! I really need your help! How much will it cost?" she replies.

That was something you haven't considered... You could easily charge her the usual price of 15 € per hour, but you could also give her a discount if she is barefoot or puts her bare feet in your lap during lessons. Or you could offer her to let you worship her feet afterwards instead of paying.

Whatever you decide, it will be one of the best tutoring sessions you have ever had!