Petitions for a merger of a district which overlaps a city, or for the establishment of the district as a subsidiary district of the city, shall be signed as follows:
(a) For a registered voter district, by either of the following:
(1) Five percent of the registered voters of the district.
(2) Five percent of the registered voters residing within the territory of the city outside the boundaries of the district.
(b) For a landowner-voter district, by either of the following:
(1) Five percent of the number of landowner-voters within the district who also own not less than 5 percent of assessed value of land within the district.
(2) Five percent of the registered voters residing within the territory of the city outside the boundaries of the district.