Arlene is single and has taxable income of $$18,000.$ Her tax liability is currently $$1,970$ She has the opportunity to earn an additional $$5,000$ if she accepts and completes a special project at work. There are no additional expenses to offset the $$5,000$ income. Consequently, Arlene will have a tax liability of $$2,570$ if she accepts the special project. Arlene has a marginal tax rate of $\%.$