62.5. The average pensionable salaries referred to in subparagraphs 1 and 2 of the first paragraph of section 62.4 are obtained by performing, in order, the following operations:(1) selecting, from among the highest annualized pensionable salaries established under sections 62.6 and 62.11, as many as are necessary to make the aggregate of the contributory periods corresponding to the years for which the salaries are selected equal to 5 or, if the aggregate is less than 5, selecting all the salaries;
(2) multiplying each salary so selected for each year by the corresponding contributory period; and
(3) dividing the sum of the salaries resulting from the multiplication by the sum of the corresponding contributory periods.