12. Authority of Tax Law Sources. Assuming that you have discovered favorable support for your position taken in a controversy with an IRS agent in each of the sources listed below, indicate how you would use these authoritative sources in your discussion with the agent. a. A decision of the U.S. District Court having jurisdiction over your case if litigated. b. Treasury Regulation. c. The Internal Revenue Code. d. A decision of the Supreme Court. e. A decision of the Court of Appeals. f. A decision heard under the small tax case procedures of the Tax Court. g. A decision of the U.S. Tax Court. h. A private letter ruling issued to another taxpayer. i. A Revenue Ruling. j. A tax article in a leading periodical