20. For the purposes of paragraphs z and aa of section 17, the categories of persons which the Minister may determine are those whose activities consist mainly of:(a) rendering personal or professional services, or
(b) selling movable property they have not produced but to which they may have made certain changes before delivery to the consumer.The determination provided for in the first paragraph shall be effected by publication of a notice in the Gazette officielle du Québec and shall have effect from the day of such publication.