Commission to call for a referendum within thirty days of the passing of such motion to endorse or reject the decision of the National Assembly and where such decision is endorsed the President shall vacate the office. (5) (6) The procedure for the conduct of such referendum shall be prescribed by an Act of the National Assembly where the life of the National Assembly is extended for any period in accordance with section 99 (2), the term of office of the President shall be extended for the same period. Whenever the speaker has requested the Chief Justice to appoint a Medical Board in accordance with section 66, to enquire into the alleged mental or physical incapacity of the president to discharge the functions of his her office, those functions shall be performed by the Vice-President or, if he or she is for any reason unable to perform those functions, by the speaker, until the Medical Board has submitted its report: Temporary exercise of 64 Of President’s functions Provided that the Vice President or the Speaker shall not take or subscribe any oath for the due execution of the office of President. Vacancy in the 65. Office of president (1) The office of President shall become vacant during the term of a Presidency . (a) (b) on the death or resignation of President or on the President ceasing to hold office under section 63, 66 or section 67. (2) Whenever the office of President becomes vacant in the circumstance set out in subsection (1), the Vice-President, or if there is no Vice-President in office at the time, the Speaker shall assume the office of President for the residue of the term of the former President. (3) Before assuming office under this section, the VicePresident or, as the case may be, the Speaker shall take the prescribed oaths for the office of President. On assuming the office of President, the Speaker shall vacate his or her