23. The capital cost of the property contemplated in section 22 is deemed to be to the partnership that portion of the capital cost of that class that the fair market value of that property on 31 December 1971 is of the fair market value of all the property of that class on such date; for that purpose, the capital cost of a class of property is equal to the lesser amount obtained after having multiplied, for each partner, his acquisition cost of the property of that class by the reciprocal of such percentage of interest in that property.