(a) Subject to subdivision (b), at least 15 days before the time set for hearing, the petitioner shall serve notice of the time and place of the hearing, together with a copy of the petition, on the following:
(1) The attorney-in-fact if not the petitioner.
(2) The principal if not the petitioner.
(b) In the case of a petition to compel a third person to honor the authority of an attorney-in-fact, notice of the time and place of the hearing, together with a copy of the petition, shall be served on the third person in the manner provided in Chapter 4 (commencing with Section 413.10) of Title 5 of Part 2 of the Code of Civil Procedure.