(3) If the fire protection district, annexing code city, and county reach an agreement on the enumerated goals, or if only the annexing code city and county reach an agreement on the enumerated goals, the code city may adopt an annexation ordinance, but the annexation ordinance provided for in this section is subject to referendum for forty-five days after its passage, provided that no referendum shall be allowed for an annexation under this section if the fire protection district, annexing code city, and the county reach agreement on an annexation for which a code city has initiated the interlocal agreement process by sending notice to the fire protection district representative and county representative prior to July 28, 2013. Upon the filing of a timely and sufficient referendum petition with the legislative body of the code city, signed by qualified electors in a number not less than ten percent of the votes cast in the last general state election in the area to be annexed, the question of annexation must be submitted to the voters of the area in a general election if one is to be held within ninety days or at a special election called for that purpose according to RCW 29A.04.330. Notice of the election must be given as provided in RCW 35A.14.070, and the election must be conducted as provided in the general election laws under Title 29A RCW. The annexation must be deemed approved by the voters unless a majority of the votes cast on the proposition are in opposition to the annexation. After the expiration of the forty-fifth day from, but excluding, the date of passage of the annexation ordinance, if a timely and sufficient referendum petition has not been filed, the area annexed becomes a part of the code city upon the date fixed in the ordinance of annexation.