3. (1) There shall be the following classes of excess profits tax authorities for the purposes of this Act, namely:- (a) the National Board of Revenue;(b) Commissioners of Excess Profits Tax;(c) Assistant Commissioners of Excess Profits Tax, who may be either Appellate Assistant Commissioners of Excess Profits Tax or Inspecting Assistant Commissioners of Excess Profits Tax;(d) Excess Profits Tax Officers;(e) Boards of Referees. (2) Every Commissioner of Excess Profits Tax, Appellate Assistant Commissioner of Excess Profits Tax, Inspecting Assistant Commissioner of Excess Profits Tax and Excess Profits Tax Officer shall be a person who is exercising the functions of Commissioner of Income-tax, Appellate Assistant Commissioner of Income-tax, Inspecting Assistant Commissioner of Income-tax and Income-tax Officer, respectively, under the Income-tax Act, 1922. (3) The National Board of Revenue shall, subject to the provisions of sub section (2), appoint such persons as Commissioners of Excess Profits Tax, Appellate Assistant Commissioners of Excess Profits Tax, Inspecting Assistant Commissioners of Excess Profits Tax and Excess Profits Tax Officers as it thinks fit and such persons shall perform their functions in respect of such cases as the National Board of Revenue may assign to them: Provided that such directions shall be made entirely at the discretion of the National Board of Revenue, and, in particular, it shall be competent for that Board to assign a case or class of cases to an officer who is not exercising in respect of that case or class of cases the corresponding functions in relation to the charge of income tax under the Income tax Act, 1922. (4) All officers and persons employed in the execution of this Act shall observe and follow the orders, instructions and directions of the National Board of Revenue: Provided that nothing in this sub section applies to a Board of Referees: Provided further that no such orders, instructions or directions shall be given so as to interfere with the discretion of the Appellate Assistant Commissioner in the exercise of his appellate functions. (5) A Board of Referees shall consist of not less than three and not more than five persons, of whom not less than one half shall be non officials having business experience, and one shall be a judicial officer who has exercised the powers of a District Judge or who possesses such qualifications as are normally required for appointment to the post of District Judge, and who has held judicial office for a period of not less than ten years. (6) Subject to the provisions of sub section (5), the Government may make rules regulating the formation, composition and procedure of Boards of Referees.