A power of appointment is exercised only:
(1) If the instrument exercising the power is valid under applicable law;
(2) If the terms of the instrument exercising the power:
(a) Manifest the powerholder's intent to exercise the power; and
(b) Subject to RCW 11.95A.230, satisfy the requirements of exercise, if any, imposed by the donor; and
(3) To the extent the appointment is a permissible exercise of the power.