Hey guys...i'm new here :)

I have a question. Think about about a BU vs SB situation. You are in the BU and opr 2.5x. You get a 3b to 8bb, you have the info SB threebets 6% out of the SB and 9% against BU.

Now, how does our mathematically correct defendingrange have to look like (1. when we take out the fact that we could 4b for value/bluff and 2. if we include a 4b-range?

If someone can give me an advice how i can calculate spots like this i would really appreciate it :).