Rule 708.5a

If a spell or ability uses the converted mana cost of a split card not on the stack to determine part of its effect, but it doesn’t perform a comparison using those values, it uses the sum of the two converted mana costs. Example: Infernal Genesis has an ability that reads, “At the beginning of each player’s upkeep, that player puts the top card of his or her library into his or her graveyard. Then he or she creates X 1/1 black Minion creature tokens, where X is that card’s converted mana cost.” If the top card of your library is Assault/Battery, which has converted mana costs of 1 and 4, when this ability resolves, you create five creature tokens. Example: Living Lore has an ability that exiles an instant or sorcery card and another ability that reads, “Living Lore’s power and toughness are each equal to the exiled card’s converted mana cost.” If Assault/Battery is exiled with the first ability, Living Lore’s power and toughness are 5/5.

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