* by managerial level
The commonly used methods for departmentalizing a firm are:
- By customer - organizing departments around customer groups.
- By product - organizing departments based on product lines or services.
- By function - organizing by business functions like marketing, operations, HR, etc.
- By geography - organizing based on geographical regions.
"By managerial level" is not a commonly used method for departmentalizing a firm. The levels of management (top, middle, lower) do not determine how a firm structures its departments.
So the answer is by managerial level.