Orders are coming in!

Well, it's been 5 days since my first commission delivery, and now i have one on order and have been asked to give a brief speech thing in young womans on cultural arts! And that's only 5 days after the first one! I'm really excited! The one on order is going to cost a bit more, seeing that their is going to be 4 children instead of two, and inevitably be a bigger size than a 9"x12", thus taking several more hours to complete. My mom and I have been researching on how to price art, seeing that i'm just starting so i don't want to overprice it- but i also want to get what my time's worth; you can price it by the hour, by how many subjects, by sq. inch, etc. So i really am not sure. This last portrait i just charged by time ($10 per hour) which came to about a hundred dollars. But from my research, that was going cheap. Any suggestions? Now if i keep getting orders, i can pay for college! (ok, at least part of it) Now that's putting a talent to good use!