cr:5.2.3d

Effects that allow the additional activation of an activated ability are additive. If an effect would allow to two or more activated abilities to be activated beyond its LIMIT, the total number of additional activations is shared between those abilities. If two or more effects would allow an activated ability to be activated beyond its LIMIT, the player chooses which of those effects apply to the activation.

Example: Tri-shot has the text “You may activate target bow you control 2 additional times this turn.” Barbed Castaway is a bow with two activated abilities with a per turn activation limit of 1. Using Tri-shot’s effect, The player may activate either ability twice, or one ability thrice and the other once.