29. Nextly, the Commission has elaborately discussed the object of introduction of Chapter XIX-A in the Act, the history behind the introduction and schematic rationalisation of the provisions of Chapter XIX-A brought about through the Finance Act, 1987 to hold that in exercising its power under Chapter XIX-A it has almost an unbridled power to arrive at a settlement. This exercise of purposive interpretation by looking into the object and scheme of the Act and legislative intendment would arise, in our opinion, if the language of the statute is either ambiguous or conflicting or gives a meaning leading to absurdity. We do not find any such problem in the provisions of the Act to which we have already referred to. Sections 234-A, 234-B and 234-C in clear terms impose a mandate to collect interest at the rates stipulated therein. The expression "shall" used in the said section cannot by any stretch of imagination be construed as "may". There are sufficient indications in the scheme of the Act to show that the expression "shall" used in Sections 234-A, 234-B and 234-C is used by the legislature deliberately and it has not left any scope for interpreting the said expression as "may". This is clear from the fact that prior to the amendment brought about by the Finance Act, 1987, the legislature in the corresponding section pertaining to imposition of interest used the expression "may" thereby giving a discretion to the authorities concerned to either reduce or waive the interest. The change brought about by the amending Act (Finance Act, 1987) is a clear indication of the fact that the intention of the legislature was to make the collection of statutory interest mandatory. In this connection, we may usefully refer to the judgment of this Court in Jaywant S. Kulkarni v. Minochar Dosabhai Shroff wherein this Court held that when the legislature changes the expression "may" to "shall" by amendment of the statute, it is clear that it intended to make the provision mandatory from the existing directory provision. Therefore, the question of the Commission relying upon external aids, for the purpose of interpretation like Wanchoo Committee Report, Discussions of Select Committee of Parliament and introduction of Chapter XIX-A in the Act, press release of the Board dated 21-5-1996 etc. are purposeless because of the clear and unambiguous language used in Sections 234-A, 234-B and 234-C and Sections 245-D(4) and (6). We notice that if only the Commission were to follow the golden rule of interpretation by giving the words of the statute their natural and ordinary meaning without unnecessarily going into a forensic exercise of trying to