Tiered deduction under Section 80C revised to a graduated scale based on aggregate eligible contributions and increased limits. Amendment to Section 80C replaces sub section (1) with a graduated deduction formula based on the aggregate of sums specified in sub section (2): full deduction up to the first threshold, a base amount plus a percentage of the excess for the middle range, and a higher base plus a lower percentage of the excess above the upper range; effective 1 April 1979. Sub section (4), clauses (ii) and (iv), have their monetary ceilings increased.