Equivalence partitioning is a technique that divides the input domain of a system into partitions or classes that are expected to behave similarly or produce similar outputs2. A test case can cover one value from each partition, as it is assumed that all values in the same partition are equivalent for testing purposes2. In this question, the groups of numbers fall into different equivalence classes based on the amount of customs duty to be paid, as shown below:
Group
Equivalence Classes
$20,000 $20,001 $30,001
No duty (up to $2,000), 10% duty ($2,001-$10,000), 12% duty ($10,001-$30,000), 17% duty (above $30,000)
$2,000 $2,001 $10,000
No duty (up to $2,000), 10% duty ($2,001-$10,000), 12% duty ($10,001-$30,000)
$2,000 $8,000 $20,000
No duty (up to $2,000), 10% duty ($2,001-$10,000), 12% duty ($10,001-$30,000)
$1,500 $2,000 $10,000
No duty (up to $2,000), 10% duty ($2,001-$10,000)