Final answer:
An activity-based costing system is most suitable for firms with multiple products, high diversity, and significant non-unit-level overhead.
Step-by-step explanation:
The firms that have plants with multiple products, high product diversity, and significant non-unit-level overhead are candidates for:
- a unit-based costing system using direct material rate.
- an activity-based costing system.
- a traditional costing system.
- a direct tracing costing system.
Out of these options, an activity-based costing system would be most suitable for firms with multiple products, high diversity, and significant non-unit-level overhead. This costing system assigns costs to products based on the activities that drive those costs, providing a more accurate representation of the actual costs incurred by each product.