81. Where a benefit is granted for a year to each spouse, such benefit shall be equal to one-half of the amount obtained pursuant to sections 73 and 75 to 77.
If the spouse of an adult for a year is no longer the adult’s spouse on 31 December of that year, the calculation provided for in the first paragraph shall, for the purposes of section 77, apply only with respect to the period of the year during which the adult had a spouse.