(b) In authorizing any such return of unabsorbed portion of premium payments, the board of directors of such a corporation may provide for an apportionment thereof among separate groups of members on the basis of earned premiums equitably classified according to major kinds of insurance.
(c) This section shall not prohibit the return of the unabsorbed portion of premium payments on an equitable basis to policyholders in other states or under reinsurance contracts.