I got the part about this being an Sn1 reaction, but my textbook's solution manual doesn't really say how to get A and B meaning that it's supposed to be an easy problem but I can't get it after googling. The question is to find A and B and the stereochemistry.

Btw, there's also a C and D formed from a third and fourth catalyst in the problem which I didn't include in this picture because I understand that part. But the molecule given as B would be impossible to react with a third catalyst (NaOMe, MeOH) wouldn't it?