Before the city may institute annexation proceedings, the City Council shall provide an opportunity for all interested persons to be heard at two (2) public hearings to be held not more than forty (40) days nor less than twenty (20) days prior to consideration of the ordinance annexing the property. If within ten (10) days after the publication of the notice required herein, more than twenty (20) adult residents who reside in the territory proposed to be annexed protest in writing to the City Secretary of the institution of the annexation proceedings, then at least one of the public hearings must be held within the area proposed to be annexed. Each written protest shall contain the name, address, and age of each signatory.