(a) Service of any civil investigative demand or petition filed under Section 140A.055 or 140A.060 may be made on any natural person by delivering a duly executed copy of the demand or petition to the person to be served or by mailing a copy by registered or certified mail, return receipt requested, to the person at the person’s residence or principal office or place of business.
(b) Service of any demand or petition filed under Section 140A.055 or 140A.060 may be made on any person other than a natural person by delivering a duly executed copy of the demand or petition to a person to whom delivery would be appropriate under state law if the demand or petition were process in a civil suit.

(c) A verified return by the individual serving any demand or petition filed under Section 140A.055 or 140A.060 setting forth the manner of service is proof of service. In the case of service by registered or certified mail, the return must be accompanied by the return post office receipt of delivery of the demand or petition.