4) Upon refusing to work or do particular work, the worker shall promptly report the circumstances of the refusal to the worker’s employer or supervisor who shall forthwith investigate the report in the presence of the worker and, if there is such, in the presence of one of, 2. (a) a committee member who represents workers, if any; 3. (b) a health and safety representative, if any; or 4. (c) a worker who because of knowledge, experience and training is selected by a trade union that represents the worker, or if there is no trade union, is selected by the workers to represent them