Answer:
d. The maintenance costs associated with the napkin folding machine.
Step-by-step explanation:
The cost that required one or more processors to produced a final product is known as joint cost
Here in the given question, the maintenance cost is not considered to be a joint cost as this cost are associated with the paper napkins
Also, the pulping, screening, rolling, etc are considered to be joint cost
Hence, the correct option is d.