Question: Under which number president did Arthur A. Ballantine become solicitor of the Internal Revenue Service?

Context paragraphs:
Pension administration in the United States: Pension administration in the United States is the act of performing various types of yearly service on an organizational retirement plan, such as a 401(k), profit sharing plan, defined benefit plan, or cash balance plan.  Increasingly these plan types are also being implemented in combination arrangements for greater contribution potential, such as the pairing of a cash balance plan with some variety of 401(k).  The basic purpose of Pension Administration is to ensure that an organizational retirement plan does not discriminate against the lower level employees while also ensuring that the plan is not used as an abusive tax shelter.  Stress tests include the average benefits test, Average Deferral Percentage, and minimum coverage.  Yearly pension administration work involves filing a Form 5500 with the Internal Revenue Service.  There are several professional designations available to those who perform this work, such as those offered by the National Institute of Pension Administrators and the American Society of Pension Professionals and Actuaries.  Pension Administration firms more often than not rely on financial brokers (or financial advisors) for their business prospects, although they do have other referral sources.  Some pension administration firms carry out the financial advisory work within an internal unit of their own company, as well as accepting referrals from an independent broker network.  Examples of firms with which these brokers are associated are Raymond James, Edward Jones Investments and Morgan Stanley.  The brokers may be employees of these firms or independent contractors.  The plan assets of the organizational retirement plans in question sometimes reside on a trading platform controlled by the administration firm.  But more often than not the assets are held by large financial institutions who provide a variety of investment options for plan participants.  Examples of large firms in this market space are Principal Financial Group, John Hancock Insurance, ING Group and Mass Mutual, although there are many others.  Plans which contain over one-hundred participants must perform an independent audit each year, necessitating yearly coordination with representatives of a public accounting firm.  In cases where a defined benefit plan is being managed the pension administration firm must employ an actuary to certify the plan's present and future benefit liabilities and compliance with minimum funding standards set by the IRS.  Pension administration firms with a large block of defined benefit plans often employ an actuary directly.  But they may also retain the actuary as an independent contractor, and this is almost certain to be the arrangement in cases where the pension administration firm only works on a small collection of defined benefit plans.  The actuary completes contribution calculations for the plan and provides a Schedule SB so that the yearly Form 5500 may be completed.  Without this Schedule the yearly filing for a defined benefit plan would be incomplete.  In addition to the Internal Revenue Service, organizational retirement plan operation and maintenance falls under the regulation of the United States Department of Labor.

Internal Revenue Bulletin: The Internal Revenue Bulletin (also known as the IRB), is a weekly publication of the U.S. Internal Revenue Service that announces "official rulings and procedures of the Internal Revenue Service and for publishing Treasury Decisions, Executive Orders, Tax Conventions, legislation, court decisions, and other items of general interest."  It began publication in 1919.

Office of the Taxpayer Advocate: The Office of the Taxpayer Advocate, also called the Taxpayer Advocate Service (TAS), is an independent office within the Internal Revenue Service, the United States Government's tax collection agency.  It is under the supervision and direction of the Taxpayer Advocate who is appointed by and reports directly to the Commissioner of Internal Revenue.  The office was created under the Taxpayer Bill of Rights 2, an act of the United States Congress which became law on July 30, 1996.  The office replaced the previous Office of the Ombudsman within the Internal Revenue Service.

John J. O'Brien (civil servant): John Joseph O'Brien (September 11, 1919 – October 16, 2001) was an American civil servant who investigated the assassination of President John F. Kennedy.  Born in Somerville, Massachusetts, O'Brien received his B.B.A. degree in law and business, cum laude, from Northeastern University, Boston.  He received his M.A. degree in the field of governmental administration from George Washington University, Washington, D.C., and in 1941 joined the Bureau of Internal Revenue.  After service in the U.S. Coast Guard, O'Brien resumed his work as an Internal Revenue Service investigator.  O'Brien was appointed as a staff member for the Warren Commission in 1963.  Their purpose was to investigate the assassination of President Kennedy.  After completion of the Warren Commission, he took the post of Assistant Chief of the Inspection Services Investigations Branch, in the National Office of Internal Revenue.

IRS Criminal Investigation Division: Internal Revenue Service, Criminal Investigation (IRS-CI) investigates potential criminal violations of the U.S. Internal Revenue Code and related financial crimes in a manner intended to foster confidence in the tax system and deter violations of tax law.  While other federal agencies also have investigative jurisdiction for money laundering and some bank secrecy act violations, the Internal Revenue Service (IRS) is the only federal agency that can investigate potential criminal violations of the Internal Revenue Code.

Tax levies: A Tax levy, under United States Federal law, is an administrative action by the Internal Revenue Service (IRS) under statutory authority, generally without going to court, to seize property to satisfy a tax liability.  The levy "includes the power of distraint and seizure by any means".  The general rule is that no court permission is required for the IRS to execute a section 6331 levy.  For taxpayers in serious debt to the IRS, the most feared weapon in the IRS arsenal is the tax levy.  Using the powers granted to the IRS in the Internal Revenue Code, the IRS can levy upon wages, bank accounts, social security payments, accounts receivables, insurance proceeds, real property, and, in some cases, a personal residence.  Under Internal Revenue Code section 6331, the Internal Revenue Service can “levy upon all property and rights to property” of a taxpayer who owes Federal tax.  The IRS can levy upon assets that are in the possession of the taxpayer, called a seizure, or it can levy upon assets in the possession of a third party, a bank, a brokerage house, etc.  All future statutory references will be to the Internal Revenue Code unless noted otherwise.

Babatunde Fowler: Dr Babatunde Fowler (born 12 August 1956) is a Nigerian public officer, tax administrator and social reformer.  He was the Executive Chairman Lagos State Board of Internal Revenue and Chief Executive Officer Lagos State Internal Revenue Service.  He is presently the Executive Chairman of the Federal Inland Revenue Service (FIRS).

Arthur A. Ballantine: Arthur A. Ballantine (1883–1960) was a 20th-century American lawyer, tax specialist, who became the first solicitor of the Internal Revenue Service and Undersecretary of the Treasury under U.S. President Herbert Hoover and later partner in what became the Dewey Ballantine law firm.

Internal Revenue Service: The Internal Revenue Service (IRS) is the revenue service of the United States federal government.  The government agency is a bureau of the Department of the Treasury, and is under the immediate direction of the Commissioner of Internal Revenue, who is appointed for a five-year term by the President of the United States.  The IRS is responsible for collecting taxes and administering the Internal Revenue Code, the federal statutory tax law of the U.S. Its duty to maximize tax revenue entails providing tax assistance to taxpayers, as well as pursuing and resolving instances of erroneous or fraudulent tax filings.  The IRS has also overseen various benefits programs, and enforces portions of the Affordable Care Act.

Herbert Hoover: Herbert Clark Hoover (August 10, 1874October 20, 1964) was an American engineer, businessman, and politician who served as the 31st President of the United States from 1929 to 1933 during the Great Depression.  A Republican, as Secretary of Commerce in the 1920s he introduced Progressive Era themes of efficiency in the business community and provided government support for standardization, efficiency and international trade.  As president from 1929 to 1933, his ambitious programs were overwhelmed by the Great Depression, which seemed to get worse every year despite the increasingly large-scale interventions he made in the economy.  He was defeated in a landslide in 1932 by Democrat Franklin D. Roosevelt, and spent the rest of his life as a conservative denouncing big government, liberalism and federal intervention in economic affairs, as Democrats repeatedly used his Depression record to attack conservatism and justify more regulation of the economy.

Supporting paragraphs: Arthur A. Ballantine Herbert Hoover
Answer: 31st