Any notice or order issued or made under this Act shall be served--
         (a) by tendering the notice or order or sending it by registered post to the person for whom it is intended or to his agent;
         (b) if the notice or order cannot be served in the manner provided in clause (a), by affixing it on a conspicuous place in the property in relation to which the notice or order is issued or made, or on some conspicuous part of the premises in which the person for whom it is intended is known to have last resided or carried on business or personally worked for gain.