A petition for annexation of territory to a city shall be signed by either of the following:
(a) Not less than 5 percent of the number of registered voters residing within the territory proposed to be annexed as shown on the county register of voters.
(b) Not less than 5 percent of the number of owners of land within the territory proposed to be annexed who also own 5 percent of the assessed value of land within the territory as shown on the last equalized assessment roll.