Final answer:
Buses may not carry more than 500 pounds of any one class of allowed hazardous materials to ensure passenger safety and compliance with transportation guidelines.
Step-by-step explanation:
The question deals with transportation regulations concerning hazardous materials on buses. Specifically, it asks about the maximum weight of a single class of allowed hazardous materials that may be carried on buses. According to the regulations, buses may not carry more than 500 pounds of any one class of allowed hazardous materials. This is important to ensure the safety of passengers and to comply with federal transportation guidelines.
Regarding part b of the question, if 20 men have a sum weight greater than 3,500 pounds, it poses a safety concern for water taxis based on similar safety limitations to those regarding the transportation of hazardous materials. Overloading vehicles, including buses or water taxis, can lead to hazardous conditions and potential accidents, underscoring the significance of adhering to prescribed safety limits.