Explosivo + Powerful Attack

[StJason]

Had a question about what happens if Madhammer uses Explosivo on a Gunner.
Now, I know that Explosivo has been ruled before as not letting special abilities of the weapon carry over. So if a weapon had Armor Piercing or a critical effect (for example), the blast wouldn't halve the armor or have any special effect in the blast.
However, Powerful Attack doesn't change the way the weapon does damage, it changes the way that focus boosts the attack. More, it says on the ability that "...all attack and damage rolls for the attack." So does this mean that:
a) You cannot use Powerful Attack on a Gunner with Explosivo (the ability is effectively removed for the duration of the spell).
b) If you use Powerful Attack on a Gunner with Explosivo, it only boosts the attack and damage of the initial attack, not the AoE.
c) If you use Powerful Attack on a Gunner with Explosivo, it boosts all attack and damage rolls, even those under the blast.
d) Something else?

[Hjelmen0]

Just for clarity: The current ruling is that the answer to your question is b