A proposal for annexation of an area to the regional district shall be initiated by a written petition. The written petition shall be signed by: at least 25% of the residents of the area to be annexed who are registered as voters in county elections; and owners of at least 25% of the assessed valuation of the real property located in the area to be annexed. If a written petition for annexation is submitted to the County Council, the chair of the County Council shall verify: the signatures on the written petition; and that the petition meets the requirements of subsection (a)(2) of this section.