What is the weekly rate for babysitting?

I was wondering what the normal weekly rate is for babysitting. It would be a Mon-Fri job from say 8am-4pm. I usually do 8 dollars an hour but I was wondering if it would be different if i charged weekly. If it was hourly, It would be close to $340. Does that sound fair or should it be cheaper? I just need to know what's fair and what the usual rate is. I'm from California.