Content AreaPiper has taxable income of $30,000 on which the income tax is $4,500. If Pipers taxable income increases to $35,000, the income tax will increase to $5,100. Which of the following is true? a. Piper's average tax rate 12 percent. b. Piper's average tax rate is higher than the marginal rate. c. Piper's average and marginal tax rates are the same. d. Piper's marginal tax rate is 15% percent