(d)Where the additional salary or additional family pension, as the case may be, relates to more than one previous year,-(i)the previous years to which the additional salary or additional family pension relates and the amount relating to each such previous year shall first be ascertained;(ii)tax shall, then, be calculated on the total income of each such previous year as increased by the amount relating to such previous year ascertained under sub-clause (i); as if the total income so increased were the total income of that previous year, and the amount by which the aggregate amount of tax in respect of the aforesaid previous years as calculated under sub-clause (ii) exceeds the aggregate amount of tax payable by the assessee in respect of the total income of the said previous years shall, for the purposes of clause (a), be taken to be the aggregate tax on the additional salary or additional family pension, under this clause.