Does anyone know how many books it takes to get 20 alchemy points?

I'm currently at 282 books and I have 17 points.

sorry if this is in the wrong place, but I think it's right...

320. Intelligence boosters don't count because they don't give AP.

Also I worked it out because you get 1AP for every 16th multiple of books read.

I'm pretty sure every 16th Intelligence point an Alchemy Point is given as long as the 16th point is provided by a book. So, you'd need 320 books to get 20 AP.

thanks to you both, I'm so glad that is raises by 16 and not 20 like I though it might :) I don't have far to go now ^^