I have a lady that has a flower bed that she would like to re-mulch. It's about 475sq. feet. How many bags of mulch would I have to have to cover it atleast 3 inches deep? I've never done any mulching before so this is all new to me. Also how would you charge for something like this and how much? How long would something like this take? Any advice you could give me would be great. Thanks!!!!