(b)[ in the case of a State Bar Council with an electorate not exceeding five thousand, fifteen members, in the case of a State Bar Council with an electorate exceeding five thousand but not exceeding ten thousand, twenty members, and in the case of the State Bar Council with an electorate exceeding ten thousand, twenty-five members, elected in accordance with the system of proportional representation by means of the single transferable vote from amongst advocates on the electoral roll of the State Bar Council:] [ Substituted by Act 60 of 1973, Section 4, for Clause (b) (w.e.f. 31.1.1974).]