7Each member of the Authority appointed by the Council under paragraph 3 (1) (b) above—
(a)shall cease to hold office when he retires at the end of his term of office as a councillor under the provisions of section 4 (3) of the [1973 c. 65.] Local Government (Scotland) Act 1973 or otherwise ceases to be a councillor unless, in the case of a councillor retiring on the day of the ordinary election of councillors, he is re-elected as a councillor at that election;
(b)may, by written notice to the Council, resign his membership of the Authority; and
(c)shall cease to hold office if at any time the Council chooses under paragraph 3 (1) (b) above to appoint another of its members to be a member of the Authority in his stead.