General

Graphic help for friends - price?

So I consider myself pretty good at graphic softwares, and I'm helping friends for years now with whatever they need (which is very good for me because it lets me practice). Tho lately I don't really feel like doing these stuff for free because they take so much time and effort, and I'm no longer this little kid with tons of free time. A good friend offered me some money now for a request he has, and he wants me to price it myself. I really have NO IDEA how much you should charge for a graphic work, and hopefully you guys do.
Thanks in advance!