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.