Notice of the hearing shall be given by all of the following:
(a) Posting a notice in three public places within the proposed improvement district.
(b) Publication of the notice once a week for two weeks in a newspaper published in the office county.
(c) Mailing a copy of the notice to the last known address of all of the owners of land in the proposed improvement district to the addresses appearing in the petition.
The notices shall be posted and mailed not less than 20 days prior to the date set for the hearing.