(a) Each year the corporation shall set apart as earned surplus not less than 10 percent of its net earnings for all the preceding fiscal year until such surplus shall be equal in value to one-half of the amount paid in on the capital then outstanding. Whenever the amount of surplus established in this Code section shall become impaired, it shall be built up again to the required amount in the manner provided for its original accumulation. Net earnings and surplus shall be determined by the board of directors after providing for such reserves as said directors deem desirable, and the determination of the directors made in good faith shall be conclusive on all persons.

(b) Corporations organized under this article shall adopt the calendar year as their fiscal year.