Rule 355.17.a
If there are multiple mandatory requirements that do not conflict, players must make a choice that will satisfy those mandatory requirements. Any individual group of such complementary mandatory requirements that contains as many non-contradictory mandatory requirements as possible forms a set. If there are two or more sets of mandatory requirements that are mutually contradictory, choose one of those sets and ignore the rest. Example: Here to Help is played from facedown at Targon’s Peak. Its controller chooses to play a Dune Drake from hand. The other battlefield is Dragon Roost. When finalizing Dune Drake, they choose to pay the [A][A] additional cost from Dragon Roost. There are two competing mandatory requirements here: playing Dune Drake to Targon’s Peak, or playing it to Dragon Roost. Dune Drake’s controller must choose one of those requirements to satisfy, and ignore the rest. Example: If Here to Help were played from hand, and its controller controlled both battlefields, if they paid the [A][A] additional cost, they would have no choice but to play Dune Drake to Dragon Roost as it would satisfy both mandatory requirements.