If at the election the question of reducing the membership of the board shall be adopted, the members in office at the next annual school election shall continue in office until the expiration of their respective terms, and members shall be elected as follows:
a. If the reduction is from nine to seven, two shall be elected at such election and two at the next annual school election thereafter;b. If the reduction is from nine to five, one shall be elected at such election, two at the first annual school election thereafter, and two at the second annual school election thereafter;c. If the reduction is from seven to five, one shall be elected at the first annual school election at which three would have been elected; andd. If the reduction is from any other number to three, one member shall be elected at such election and at each annual school election thereafter. All members so elected shall be elected for terms of three years.