50.3. The average pensionable salaries referred to in subparagraphs 1 and 2 of the first paragraph of section 50.2 are obtained by performing, in order, the following operations:(1) selecting, from among the highest annualized pensionable salaries, as many as are necessary to make the aggregate of the contributory periods corresponding to the years for which the salaries are selected equal, in the case where the employee is entitled to a pension under the first paragraph of section 49, to 3 or, if the aggregate is less than 3, selecting all the salaries, or, in the case where the employee is entitled to a pension under the second paragraph of that section, 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.