A bus is carrying 95 pounds each of five allowed hazardous-material classes. A shipper wants to add 30 pounds of a sixth allowed class. What is the main problem?

1. The total would become 505 pounds, above the 500-pound total limit
2. The sixth class automatically makes the bus a hazmat tanker
3. A bus may carry only one class of allowed hazardous material
4. The per-class limit would be exceeded for all six classes