combining "extra head" evolution with doubled "bite" evolution

[caribet]

Can you settle an unresolvable argument we have:

in the APG, the Summoner and Evolutions are introduced. The Evolution "Bite" p.60 gives damage for a Bite attack by size, then states "if the eidolon already has a bite attack, this evolution allows it to deal 1-1/2 times its Strength modifier on damage rolls with its bite".

So far so good, if you only have one head!

Ultimate Magic introduces "extra head" p.77 The extra head doesn't have any additional attack unless you add Bite, Gore, or Breath.

So if I start with a Quadruped which has one head, and Bite, initially.
* I could add a Head to the Quadruped, and still have only the base Bite.
* I could add a Bite to the 2nd head and have 2 base-Str bites
*or*
* I could add Bite to the first head and have one 1-1/2 Str bite

what happens if I add Bite to the 2nd head, then add Bite a further time, to boost damage to 1-1/2 Str?

does it
a) affect all Bites on all Head that already have a Bite?
or
b) affect one chosen head-with-bite, and you need to buy a doubled-bit for each head to have them all with 1-1/2 Str?

[Zahmahkibo]

The language is somewhat ambiguous, but considering Bite was written at a time when eidolons could not have more than one head, b) is the most reasonable interpretation.

[Archaeik]

The language in the evolution only ever references a bite as singular.

Considering that the Reach evolution was clarified to be a single attack (even if it's just 1 claw), B is almost certainly the answer in this case.