(1) The prohibitions of the Age Discrimination in Employment Act shall be limited to the employment of individuals who are forty years or more of age.

(2) Nothing contained in the act shall be construed as making it unlawful for an employer, employment agency, or labor organization (a) to take action otherwise prohibited under the act when age is a bona fide occupational qualification reasonably necessary to the normal operation of the particular business, or when the differentiation is based on reasonable factors other than age, such as physical conditions; or (b) to discharge or otherwise discipline an employee for good cause.