Patricia has taxable income of $40,000 on which she pays income tax of $4,604. If Patricia's taxable income increases by $2,000, she will pay an additional tax of $440. What is Patricia's marginal tax rate?

a. 25.00 percent

b. 14.84 percent

c. 15.00 percent

d. 22.00 percent

e. None of these choices are correct.