vanity rough in for drain

I am installing a vanity with a sink that sits on top of the vanity. The vanity has two banks of drawers one on either side with a 48 inch opening between them. The front of this opening will have a skirt to hide the trap etc. Say about 12 inches. What height should I rough in my waste?

Thanks for any help, King

I would set the fixture against the wall and gauge this so you know where to rough-in the piping.