For "A":
The accepted penalty for the holding foul by B would be a Basic Spot/3 and 1 enforcement. The foul occurs during a running play that ends behind the neutral zone. The previous spot is the Basic Spot, and fouls by the opponents of the team in possession (at the time of the foul) are penalized from the Basic Spot. 10 yards, repeat the down. A, 1/10, 50.
For "B":
If accepted, the penalty for the holding foul by A would be penalized from the previous spot (by rule). 10 yards, repeat the down. A, 1/20, A-30. But, there is a high likelihood that B will decline this penalty, on the assumption that ball becomes dead somewhere behind the NZ, and obviously declined, if 10 or more yards behind the NZ.
Robert