(a) A corporation shall set apart as earned surplus not less than 10 percent of the corporation's net earnings each year until the surplus, with any unimpaired surplus paid in, is equal to one-half of the amount paid in on the shares then outstanding. The surplus shall be kept to secure against losses and contingencies. If the surplus becomes impaired, the surplus shall be reimbursed in the manner provided for its accumulation.
(b) Net earnings and surplus shall be determined by the board of directors after providing for the required reserves as the directors consider advisable. A good faith determination of net earnings and surplus by the directors under this subsection is conclusive.