Elvia McCann and Leone McCann (plaintiffs) attended a four-day seminar in Las Vegas at the invitation of Mrs. McCann’s employer, an insurance company. The invitation went to Mrs. McCann and 46 other agents, out of 400 agents in all, who had met their sales quotas for the preceding year. The company paid for the McCanns’ transportation, lodging, and other expenses. Although the company’s agents were based in Louisiana, seminars were never held in New Orleans because the city was too familiar to their agents. Instead, the company always selected venues based on excitement and charisma and made an array of entertainment and recreational activities available to seminar attendees. For Mrs. McCann, the seminar in Las Vegas included a few hours of panel discussions, group meetings, and speeches by company officials. However, by far the greater portion of Mrs. McCann’s time, and all of her husband’s time, was spent on meals, parties, shows, and leisure activities that were either paid for or facilitated by the company. Most eligible agents attended the seminar but were not required to do so and were not penalized in any way for non-attendance. The Internal Revenue Service audited the McCanns’ income-tax return and issued a deficiency notice for failing to report the value of the seminar as gross income. The McCanns paid back taxes on the fair market value of the Las Vegas trip and then brought suit against the United States (defendant) for repayment.