Answer:
well, simply, it would be $2520.
in reality, an income tax does not work that simply. income taxes are figured using brackets, where (just making up numbers) the first $15000 might be taxed at 2%, earnings between $15,001 to $30,000 are taxed at 4%, and so on.
Thus, without knowing the tax tables to know the different rates and brackets, it's impossible to give an answer.
But in straight math terms, 6% of $42,000 is $2520
42000×.06= 2520