137.2. For the calculation of the second additional portion of the basic monthly amount of the surviving spouse’s pension, the amount to be used is, depending on the contributor’s situation for the month of his death,
(a) in the case of a contributor to whom a retirement pension was payable, the amount of that pension for the month of his death, established without taking account of the amounts calculated as provided in subparagraphs a and b of the first paragraph of section 120 and adjusted in accordance with section 119, any partition effected under sections 158.3 to 158.8 or a similar plan, any adjustments provided for in sections 120.1 and 120.2, or any additional pension established under subparagraphs a and b of the second paragraph of section 120.3; and
(b) in other cases, an amount equal to 33.33% of the contributor’s average second additional monthly pensionable earnings, calculated as provided in section 116.2.2, for the year of his death.
The amount obtained is adjusted by multiplying it by the ratio between the Pension Index for the year including the month for which the second additional portion of the basic monthly amount is established and the Pension Index for the year of the contributor’s death.