(b)every person who was at the time of such discontinuance a partner of such firm or a member of such association or family shall notwithstanding such discontinuance, be liable severally and jointly for the payment of the tax payable by such firm, association or family, whether such assessment is made prior to or after such discontinuance and, subject as aforesaid the provisions of this Act shall apply as if every such person or partner were himself a dealer ;