4. (1) If an amalgamation or total annexation occurs after the date of the last census recognized under section 3, the population of the new or the subsisting municipality is the total of the population of each of the municipalities amalgamated or affected by the annexation, as established in that census.
(2) If a partial annexation occurs after the date mentioned in subsection 1, the population of each municipality affected by the annexation is the population given in the census referred to in subsection 1, plus or minus, as the case may be, the population of the annexed territory, as determined by the Gouvernement.
(3) If the population of a municipality affected by an amalgamation or annexation is not given in the census referred to in subsection 1, it shall be determined by the Gouvernement.