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