Rayquaza EX & Prism Energy

[PidgeyCornerFTW]

:fire::lightning: Dragon Burst 60x

Discard all basic :fire: Energy or all basic :lightning: Energy attached to this Pokémon. This attack does 60 damage times the number of Energy cards you discarded.

I'm a little confused on the ruling for this attack and Prism energy. For example, if Rayquaza EX has 1 prism and 2 :lightning: attached to it, can I choose to do 180 damage and discard all 3 energy? Or can I just discard the 2 :lightning: and do 120 damage?

Thanks in advance!

 

[PokePop]

too soon.