(a) An employee may voluntarily agree to forego any rest period or meal period. The employer has the burden of proving the existence of the agreement with the employee.
(b) An employer may apply to the Commissioner of Labor for an exemption from providing to all or to one or more defined categories of his employees one or more benefits conferred in this section. The Commissioner of Labor may grant the exemption, if he believes that the employer has shown sufficient evidence that business necessity precludes providing the benefits, and that the exemption would not materially affect the welfare or comfort of employees.
(c) The Commissioner of Labor may by regulation exempt a defined category of employers from providing to all or to one or more defined categories of their employees one or more benefits conferred by sections 20c and 20b, upon his own motion or upon the application of an association of employers. Each such application must be considered at a hearing and may be granted, if the Commissioner of Labor finds that business necessity precludes providing that particular benefit or benefits to the employees affected, and that the exemption would not materially affect the welfare or comfort of employees.