Hi, little Kim, I didn't see your last message before writing my last one.
I think AP book is wrong. But it's really hard to prove it.
Anyway, DPD is against me and against you.
You can check
ayudar at:
http://buscon.rae.es/dpdI/
You will find that, among others, there are two uses of this verb, one with
con, another one with
en. So, according to this, both will be OK. The question is who uses that and where.
The point is dialectal differences.
So, what I understand is that AP book shouldn't deny one of the possibilities. Even it shouldn't make you think you have to choose one between two. But that's another story.
