(a) The Board may deal with and enter into written contracts with the employees of the Authority through accredited representatives of such employees or representatives of any labor organization authorized to act for such employees, concerning wages, salaries, hours, working conditions and pension or retirement provisions; provided, nothing herein shall be construed to permit hours of labor in excess of those provided by law or to permit working conditions prohibited by law. In case of dispute over wages, salaries, hours, working conditions, or pension or retirement provisions the Board may arbitrate any question or questions and may agree with such accredited representatives or labor organization that the decision of a majority of any arbitration board shall be final, provided each party shall agree in advance to pay half of the expense of such arbitration. No contract or agreement shall be made with any labor organization, association, group or individual for the employment of members of such organization, association, group or individual for the construction, improvement, maintenance, operation or administration of any property, plant or facilities under the jurisdiction of the Authority, where such organization, association, group or individual denies on the ground of race, creed, color, sex, religion, physical or mental disability unrelated to ability, or national origin membership and equal opportunities for employment to any citizen of Illinois.