4. Which of the following statements is an example of normative economics? a. The United States should pass a value-added tax, since this is a tax that will work best. b. A value-added tax will add $10 billion to the administrative costs of the U.S. tax system. c. It can be demonstrated that value-added taxes increase the tax burden on less wealthy households. d. A value-added tax would generate $200 billion in revenue each year. e. Two other countries have value-added tax systems