Durden Soap incurs the following indirect costs per month: Indirect Labor Employee Insurance 220 Durden expects to manufacture 80,000 units during the coming year. Why do these fixed costs present a special problem to Durden? O a. by denition, fixed costs do not vary as volume changes. 0 b. by denition, these costs increase regardless of volume. 0 c. the number of units could increase, increasing fixed costs. 0 d. the number of claims on employee insurance could increase insurance costs