Jean Received a Commission of $7,000 from Her Employer

Jean received a commission of $7,000 from her employer.How is the federal withholding tax on this payment calculated if she also earns semimonthly wages of $3,500?

A) If taxes have already been withheld from Jean's regular wages,the commission is added to the wages and the entire amount is subject to withholding at a rate of 25%.
B) If taxes have already been withheld from Jean's wages,the commission is taxed at a flat rate of 25%.
C) If taxes have already been withheld from Jean's wages separately,the commission is added to the wages and federal taxes are withheld on this combined amount.Any excess taxes withheld this pay period will be refunded to Jean on her next paycheck.
D) If taxes have already been withheld from Jean's wages separately,the commission is subject to backup withholding of 28%.