Exterra riders, what does it take to qualify for Tahoe?

Having tasted my first bit of success, an age group second, in Exterra this weekend, I was reading about qualifying for Tahoe. Am I correct that only your best three races count? If so, if you got an AG first at a regional championship and two more AG firsts you could get 250 points, 100 for the regional and 75 for each of the local races. It looks to me that that is the max. Am I right? What number does it really take to get there? I’m thinking that I’ll be doing a lot of Extera’s next year, the short runs on dirt really agree with my knees and the change from the crowding at road tri’s is like a breath of fresh air.