The Authority shall not make any material change in the scheme approved under sub-section (5) of section 14 without the prior approval of the Central Government.
     Explanation.--For the purposes of this section, "material change" means an increase in the cost of the scheme by more than twenty per cent. of its cost or a change in the benefit and cost ratio which either makes the cost component in the ratio exceeds the benefit or reduces the benefit component by more than twenty per cent.