9. To be authorized to carry on professional activities in accordance with this Regulation, a hearing-aid acoustician carrying on professional activities within a partnership or joint-stock company must furnish and maintain security, on behalf of the partnership or joint-stock company, by means of an insurance or suretyship contract, or by joining a group plan contract entered into by the Order, against the liability of the partnership or joint-stock company arising from fault on the part of a hearing-aid acoustician in carrying on professional activities within the partnership or joint-stock company.