REPLY: I don't usually disagree with BBR, but I think I'll make an exception here.
I agree with kentref...
The batting by B is illegal. Flag it. If A declines the penalty for B's foul, it will be their ball, 1st and Goal at B's 1. If they accept the penalty, remember it was a
running play. Penalize B half the distance from the end of A23's run. A's ball, 1st and goal from B's 5. It will not be a safety.