Answer:
c. product cost and factory overhead cost
Step-by-step explanation:
A janitor's wage is a maintenance overhead cost, as it is the wage of a maintenance staff member. As such, it does go in the total product cost, but not in the form of direct labor cost. Instead, it belongs to factory overhead costs, together with other factory maintenance costs.
This is not a direct labor cost, as it is not directly involved in the manufacturing process. Instead, it is supporting it.