(a) The directors of a domestic mutual insurer may from time to time apportion and pay to its members dividends only out of that part of its surplus which is in excess of its required minimum surplus.
(b) The dividends shall be paid or credited to policyholders according to such reasonable classification of its policies as the directors may in their discretion from time to time establish. No dividend shall be paid which unfairly discriminates between policies within the same classification.
(c) No dividend, otherwise earned, shall be made contingent upon the payment of renewal premium on any policy.