Notice of hearing on a protested application shall be given by mailing notice not less than 20 days before the date of hearing to both the applicant and protestant by registered mail.

The notice of hearing on a protested application shall state the names of the applicant and protestant, the time and place fixed for the hearing, and such other appropriate information as may be deemed advisable by the board.

If a hearing is held on an unprotested application, notice of hearing shall be given by mailing notice not less than 20 days before the date of hearing.