A joint resolution or petition shall prescribe the form or plan of government of the proposed consolidated city, or shall provide that a ballot proposition to determine the form or plan of government shall be submitted to the voters of the cities proposed to be consolidated. The plans or forms of government include: Mayor/council, council/manager, and commission. If a commission form or plan of government is prescribed or chosen by the voters, the commission shall be subject to chapter 35.17 RCW and the noncharter code city shall be assumed to have had a commission plan or form of government prior to its becoming a noncharter code city, as provided in RCW 35A.02.130. However, three commissioners would be elected at the election provided in RCW 35.10.480.