Final answer:
Unit fixed costs decrease in value with an increase in output units because the total fixed cost is spread over more units, resulting in a lower fixed cost per unit.
Step-by-step explanation:
The question is about unit fixed costs and their behavior with respect to output. Fixed costs, by definition, do not change with an increase or decrease in the number of units produced. Therefore, fixed costs on a per-unit basis will decrease as the number of units produced increases. This is because the same total fixed cost is spread over a larger number of units, leading to a lower fixed cost per unit.
Option (a) suggests that unit fixed costs lead to more effective business decisions when compared to total fixed costs; however, it's the combination of fixed and variable costs that often inform decision-making. Option (b) is inaccurate because the contribution margin is calculated by deducting variable costs per unit from the selling price per unit, not by using fixed costs. Option (c) is also incorrect as fixed costs are not a causal factor for sales; they are costs that must be covered by the business irrespective of sales volume. Lastly, option (d) is indeed true: Unit fixed costs decrease in value with an increase in output units, due to the spreading effect of total fixed costs over more units.