Rule 601.5 · Casting Spells

While announcing the choices of any targets and/or the division or distribution of any effects as described in rules 601.2c–d, some options may be available to a player only if other choices are made later in spellcasting process. In that case, the spell’s controller may consider any other choices to be made during that process, including the choice of any objects that may be used to pay costs for that spell.