(a) Upon the liquidation of a domestic mutual insurer, its assets remaining after discharge of its indebtedness, policy obligations, repayment of contributed or borrowed surplus, if any, and expenses of administration, shall be distributed to existing persons who were its members at any time within 36 months immediately preceding the date the liquidation was authorized or ordered, or date of last termination of the insurer's certificate of authority, whichever date is the earlier.
(b) The distributive share of each member shall be in the proportion that the aggregate premiums earned by the insurer on the policies of the member during the combined periods of that member's membership bear to the aggregate of all premiums earned on the policies of all the members. The insurer may, and if a life insurer shall, make a reasonable classification of its policies held by the members, and a formula based upon the classification, for determining the equitable distributive share of each member. The classification and formula is subject to the approval of the director.