Use the following table to answer the questions.
Annual Income Tax Liability
$15,000........................................$0
30,000......................................4,500
45,000....................................11,250
60,000....................................21,000
75,000....................................30,000
a. What is the average tax rate at each income level?
b. Based on these data, is the tax progressive or regressive? Briefly explain.
c. Is it possible based on these data to determine the marginal tax rate of someone earning $65,000 per year? Briefly explain.