(2) The plan of division of properties provided for in subsection (1) of this section shall be arrived at by giving consideration to the assessed valuation of the other district as a whole, the assessed valuation of the territory to be annexed, the types of properties and their location and intended use. If a plan of division of properties is agreed upon, the plan shall be reduced to writing and, if the proposed annexation is approved by the electors, shall be binding upon the districts party to the plan and upon all other interested persons. [Amended by 1957 c.671 §7; 1969 c.563 §20; 1971 c.727 §123]