What follows is an opinion from a United States Court of Appeals.
Your task is to identify the issue in the case, that is, the social and/or political context of the litigation in which more purely legal issues are argued. Put somewhat differently, this field identifies the nature of the conflict between the litigants. The focus here is on the subject matter of the controversy rather than its legal basis.
Your task is to determine the specific issue in the case within the broad category of "economic activity and regulation".

Opinion:
RUSSELL & CO. v. SANCHO.
No. 3236.
Circuit Court of Appeals, First Circuit.
Nov. 9, 1937.
George M. Wolfson, of New York City (Francis E. Neagle and Rounds, Dilling-ham, Mead & Neagle, all of New York City, on the brief), for appellant.
William C. Rigby, of Washington, D. C. (B. Fernandez Garcia, Atty. Gen., of Puer-to Rico, and Nathan R. Margold, Sol. for Dept, of Interior, of Washington, D. C., on the brief), for appellee.
Before BINGHAM, WILSON, and MORTON, Circuit Judges.
PER CURIAM.
This court is unable to say that the Supreme Court of Puerto Rico was clearly wrong in ruling and holding that the machine described in plaintiff’s complaint was a tractor and taxable as such under -the provisions of section 16, par. 8, of the Internal Revenue Law of Puerto Rico 1925, No. 85, as amended by Act No. 83, § 16, par. 8, of 1931.
In this situation the plaintiff cannot recover the additional tax which it paid under protest, and the judgment of the court below will be affirmed.
The judgment of the Supreme Court of Puerto Rico is affirmed, with costs to the appellee in this court.

Question: What is the specific issue in the case within the general category of "economic activity and regulation"?

Choices:
taxes, patents, copyright
torts
commercial disputes
bankruptcy, antitrust, securities
misc economic regulation and benefits
property disputes
other

Answer: 0