Indicate whether each of the following costs of a motorcycle manufacturer would be classified as direct materials cost, direct labor cost, or factory overhead cost:

Cost Classification

a$.$ Motorcycle engine

b$.$ Depreciation of robotic assembly line equipment

c$.$ Brake pads

d$.$ Glass for windshield

e$.$ Tires

f$.$ Salary of quality control inspector

g$.$ Motorcycle seat

h$.$ Safety helmets and masks for assembly line workers

i$.$ Wages of assembly line workers