How much should I charge (hourly) for my first web design job?

Hey,

A couple of people from the village I live in sell decorated towels and want to expand their reach beyond our town. They want me to do their website for them, and they asked me how much I'd want for it (per hour).

All the work I've done in the past has been either for myself, small things for friends for free, or a couple of jobs in my extended family; all places I wasn't really thinking about payment much.

Any ideas?

PS: I'm 16, so I'm not going to charge them the $100s/ hour I'm seeing professionals charge online (the reason they probably asked me in the first place is because I'll be a lot cheaper than most alternatives.)