The commissioner shall cause a notice of such assessment order setting forth a brief summary of the contents of such order to be:

(1) Published in such manner as shall be directed by the court; and

(2) Enclosed in a sealed envelope, addressed and mailed postage prepaid to each member or subscriber liable thereunder at his or her last known address as it appears on the records of the insurer, at least twenty days before the return day of the order to show cause provided for in RCW 48.31.340.