If the board of supervisors determines, with respect to a petition for annexation filed in conformity with this chapter, that
(a)
The petition for annexation should be granted in whole or in part, pursuant to Chapter 12 (commencing with Section 19210), and
(b)
It is just and equitable, and in the public interest, that the proposed temporary zone be formed, and
(c)
That the petition was signed by resident taxpayers representing 60 percent or more of the total assessed valuation of all taxable property within the area therein proposed to be annexed,
the board, in addition to those proceedings required by Chapter 12, shall by resolution entered in its minutes, declare the annexed territory established as a temporary zone with boundaries coterminous with the boundaries of the territory annexed, designating the zone by an identifying name or number; and shall specify the purposes and duration thereof, not to exceed three years from the beginning of the next ensuing fiscal year in which a special tax or assessment levy may be made therein.