Which of the following groups of amounts falls into three different equivalence classes for customs duty calculations?

To determine which group of amounts falls into three different equivalence classes for customs duty calculations, it's important to understand the concept of equivalence classes. In this context, an equivalence class can comprise amounts that may fall within the same range or category for duty calculations.

In the amounts given in choice C: $2,000, $8,000, and $20,000, each amount represents a distinct bracket that may trigger different customs duties. Often, customs duties are calculated based on specific thresholds or limits, and as the amount increases, these thresholds change, leading to different rates or classes.

$2,000 represents one class, $8,000 represents a higher class, and $20,000 falls into an even higher class. Each of these amounts is distinguishable from the others based on the customs duty regulations that apply to their respective ranges, thus they fall into three different equivalence classes.

In contrast, the other choices do not effectively represent three unique equivalence classes. Some may contain amounts that could belong to the same customs duty bracket or fall too close together to be classified distinctly under duty calculations. Therefore, choice C successfully meets the requirement for three different equivalence classes.