What follows is an opinion from a United States Court of Appeals. Your task is to identify the federal agency (if any) whose decision was reviewed by the court of appeals. If there was no prior agency action, choose "not applicable".

Opinion:
COMMISSIONER OF INTERNAL REVENUE v. WIDENER (three cases).
Circuit Court of Appeals, Third Circuit
June 20, 1929.
Nos. 4001, 4002, 4003.
Mabel Walker Willebrandt, Asst. Atty. Gen., and John Vaughan Groner and Bar-ham R. Gary, both of Washington, D. C. (C. M. Charest, General Counsel, and Shelby S. Faulkner, Sp. Atty. Bureau of Internal Revenue, both of Washington, D. C., of counsel), for appellant.
Ellis Ames Ballard, William R. Spofford, and Schoffleld Andrews, all of Philadelphia, Pa. (Ballard, Spahr, Andrews & Ingersoll, of Philadelphia, Pa., of counsel), for appellees.
Before BUFFINGTON and WOOLLEY, Circuit Judges, and THOMSON, District Judge.
BUFFINGTON, Circuit Judge.
These cases present the question whether the Board of Tax Appeals erred in holding, as it did, that the racing stables of these taxpayers were operated as a “business,” or a “transaction entered into for profit,” within the meaning of the Revenue Acts of 1918 and 1921 (40 Stat. 1057, 42 Stat. 227). The Board of Tax Appeals held they were, and allowed reductions for losses thereby sustained. Thereupon the Commissioner took this appeal. The facts are not in dispute, and the warrant for the conclusions drawn therefrom by the Board are so fully and satisfactorily set forth in the record as to make a restatement by this court unnecessary.
Finding no error, judgment of the Tax Board is affirmed.

Question: What federal agency's decision was reviewed by the court of appeals?

Choices:
Benefits Review Board
Civil Aeronautics Board
Civil Service Commission
Federal Communications Commission
Federal Energy Regulatory Commission
Federal Power Commission
Federal Maritime Commission
Federal Trade Commission
Interstate Commerce Commission
National Labor Relations Board
Atomic Energy Commission
Nuclear Regulatory Commission
Securities & Exchange Commission
Other federal agency
Not ascertained or not applicable

Answer: 13