The mediation proceedings under this Act shall be deemed to terminate—

   (a)  on the date of signing and authentication of the mediated settlement agreement; or

   (b)  on the date of the written declaration of the mediator, after consultation with the parties or otherwise, to the effect that further efforts at mediation are no longer justified; or

   (c)  on the date of the communication by a party or parties in writing, addressed to the mediator and the other parties to the effect that the party wishes to opt out of mediation;

   (d)  on the expiry of time limit under section 18.