Double Rainbow Damage

[Dek]

I was thinking of this about 2 days ago, and im finally able to ask some questions about Double Rainbow Energy:

1. Would I be able to declare 2 Darkness energy if I were to attach DRE to a Darkness/Magma/Aqua/Dark(from Rocket/ND set) Pokemon?

2. If yes, how would damage be calculated?

a. Would you add the 20 damage (10 for each "Darkness Energy") and then subtract 10?
OR
b. Would you subtract 10 from the total damage and then the 20 damage (10 for each "Darkness Energy")

 

[PokePop]

1. Would I be able to declare 2 Darkness energy if I were to attach DRE to a Darkness/Magma/Aqua/Dark(from Rocket/ND set) Pokemon?
Yes

2. If yes, how would damage be calculated?

a. Would you add the 20 damage (10 for each "Darkness Energy") and then subtract 10?
No

b. Would you subtract 10 from the total damage and then the 20 damage (10 for each "Darkness Energy")
No

It would be: c. Subtract 10 damage. Don't add any.

While DRE can be counted as Darkness energy, there is no text on the card saying anything about giving a Damage Bonus.

It's not the Darkness energy itself that gives a damage bonus, it's the text on the Special Energy Card called Darkness Energy that gives a damage bonus.
No text, no bonus.