You are right, I'm the idiot and didn't read the question carefully... About the actual question, I don't think that's very well specified in this form. You co

You are right, I'm the idiot and didn't read the question carefully... About the actual question, I don't think that's very well specified in this form. You could have A~Beta0 where Beta0 is very concentrated around let's say 0.5, and then find a B~Beta1 where Beta1 has 71% of its weight above 0.5. That would be a pretty good approximation for it, in fact as close as you want if you increase sample size of A. I can't verify this, but I think finding Beta1 should be easy. Obv this is not what you are looking for though, because this would require A to have a much larger sample size than B. I guess we should add some restriction, like similar sample sizes.