(a) Notice shall be served upon each contestee at least twenty (20) days prior to the date set for hearing.
(b) Service of the Notice or of any other document or pleading required to be served may be made either personally or by mailing to the last known address of the contestee. If personal service is made, the return of service shall be made by the certification of the person who made such service. Such return of service may be filed with the Commission prior to the commencement of the hearing.
040-27 Wyo. Code R. § 27-4