What follows is an opinion from a United States Court of Appeals.
Intervenors who participated as parties at the courts of appeals should be counted as either appellants or respondents when it can be determined whose position they supported. For example, if there were two plaintiffs who lost in district court, appealed, and were joined by four intervenors who also asked the court of appeals to reverse the district court, the number of appellants should be coded as six.
When coding the detailed nature of participants, use your personal knowledge about the participants, if you are completely confident of the accuracy of your knowledge, even if the specific information is not in the opinion. For example, if "IBM" is listed as the appellant it could be classified as "clearly national or international in scope" even if the opinion did not indicate the scope of the business. 

Your task concerns the first listed appellant. The nature of this litigant falls into the category "private business (including criminal enterprises)", specifically "manufacturing". Your task is to determine what subcategory of business best describes this litigant.

Opinion:
UNITED PRODUCING COMPANY, Inc., a corporation, Appellant, v. PANHANDLE EASTERN PIPE LINE COMPANY, a corporation, Appellee.
No. 4703.
United States Court of Appeals Tenth Circuit.
Sept. 8, 1954.
William J. Holloway, Jr., and Y. P. Crowe, Oklahoma City, Okl. (Embry, Johnson, Crowe, Tolbert & B oxley, Oklahoma City, Okl., H. W. Stubbs, and Stubbs & Wesley, Ulysses, Kan., on the brief), for appellant.
Mark H. Adams, Wichita, Kan., and William I. Robinson, Tulsa, Okl. (Edward H. Lange, Kansas City, Mo., and Adams, Jones, Robinson & Manka, Wichita, Kan., on the brief), for appellee.
Before BRATTON, MURRAH and PICKETT, Circuit Judges.
PER CURIAM.
The case of Columbian Fuel Corp. v. Panhandle Eastern Pipe Line Co., 176 Kan. 433, 271 P.2d 773, was decided after entry of the judgment herein. On the authority of that case, the judgment is vacated and the cause is remanded.

Question: This question concerns the first listed appellant. The nature of this litigant falls into the category "private business (including criminal enterprises)", specifically "manufacturing". What subcategory of business best describes this litigant?

Choices:
auto
chemical
drug
food processing
oil refining
textile
electronic
alcohol or tobacco
other
unclear

Answer: 4