In a system designed to work out the tax to be paid: An employee has ?4000 of salary tax free. The next ?1500 is taxed at 10%. The next ?28000 after that is taxed at 22%. Any further amount is taxed at 40%. To the nearest whole pound, which of these is a valid Boundary Value Analysis test case?

Boundary Value Analysis tests values at the edges of equivalence partitions. The tax boundaries are at $4000, $5500 ($4000+$1500), and $33500 ($4000+$1500+$28000). For the upper boundary of the 22% bracket, \$33500 is the last value taxed at 22%, and \$33501 is the first value taxed at 40%. This makes \$33501 a valid boundary test case for the transition to the highest tax rate. Option A (\$28000) and C (\$32001) are mid-range values, not boundaries. Option D (\$1500) is not a tax boundary.