(a) The directors of a domestic mutual insurer on the cash premium plan may from time to time apportion and pay to its members as entitled thereto, dividends only out of that part of its surplus funds which are in excess of its required minimum surplus and which represent net realized savings and net realized earnings from its business.
(b) Any classification of its participating policies and of risks assumed thereunder which the insurer may make shall be reasonable. No dividend shall be paid which is inequitable, or which unfairly discriminates as between such classifications or as between policies within the same classification.
(c) No dividend, otherwise earned, shall be made contingent upon the payment of renewal premium on any policy.