Piper has taxable income of $30,000 on which the income tax is $4,500. If Piper's taxable income increases to $35,000, the income tax will increase to $5,100. Which of the following is true? Question 20 options: a) Piper's average tax rate is higher than the marginal rate. b) Piper's average tax rate 12 percent. c) Piper's marginal tax rate is 15% percent. d) Piper's average and marginal tax rates are the same