"The ADA does except employers from the 'reasonable accommodatio' requirement where the employer 'can demonstrate that the accommodation would impose an undue hardship on the operation of the business of such covered entity.' § 12112(b)(5)(A). However, even with this exception, the accommodation duty far exceeds what is constitutionally required in that it makes unlawful a range of alternate responses that would be reasonable but would fall short of imposing an 'undue burden' upon the employer. The Act also makes it the employer's duty to prove that it would suffer such a burden, instead of requiring (as the Constitution does) that the complaining party negate reasonable bases for the employer’s decision. See ibid."