Sec. 5. Service of notices.
   Whenever notice is required to be given and service to be made upon the owner of said building it shall be given in the following manner:
   (a)   By leaving said notice or order in the hands or possession of said owner; or,
   (b)   By mailing said notice or order by certified mail, to the last known address of the said owner, and time shall be computed from the time the order is so mailed; or,
   (c)   By posting said order or notice on said building in a conspicuous place. (P.L. 1959, ch. 72, § 5.)