B. how much total manufacturing cost is an indirect cost that cannot be easily traced to the manufacturing department

Given the object cost is the manufacturing department, we should consider direct cost all the manufacturing cost thus; material, labor, and overhead are direct costs linked to whether there is or isn't a manufacturing department. There is none indirect manufacturing cost.

Indirect manufacturing cost is determined when the object cost is the units of production. There the overhead cannot be linked directly into the unit thus, accounting creates a method to allocate the overhead among the units.