Callahan Construction Co. and the Carpenters’ union just concluded negotiations for a new collective agreement covering Callahan’s employees. Before shaking hands to “seal the deal” the union representative informs Callahan’s chief negotiator that the union will not agree to the final deal unless the employer joins and pays dues to the Green Builders Association and agrees to promote energy-efficient and environmentally friendly construction techniques. Is the union’s last demand over a mandatory subject for bargaining? Is the Union bargaining in bad faith? Explain your answer.