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 is taxed at 22%. Any further amount is taxed at 40%. Which of these groups of numbers would fall into the same equivalence class?

a) £4800; £14000; £28000
b) £5200; £5500; £28000

c) £5800; £28000; £32000
d) £28001; £32000; £35000