The service of the notice of declaration of a structure as unfit for human habitation and order to vacate shall be made in the following order:

A. By delivery to the owner personally, or by leaving the notice at the usual place of abode of the owner with a person of suitable age and discretion; or

B. By certified or registered mail addressed to the owner at his last known address with postage prepaid thereon; or

C. By posting and keeping posted for twenty-four hours a copy of the notice in placard form in a conspicuous place on the premises to be vacated. (Ord. 1977-14 § 13-8, 1977)