The pilot premiered on September 10, 1993, and reached 12 million viewers. As the season progressed, ratings began to increase and the season finale garnered 14 million viewers. The first season ranked 105th out of 128 shows during the 1993–94 United States network television schedule television season. The series second season increased in ratings—a trend that would continue for the next three seasons—and finished 63rd out of 141 shows. These ratings were not spectacular, but the series had attracted enough fans to receive the label "cult hit", particularly by Fox standards. Most importantly it made great gains among the 18-to-49 age demographic sought by advertisers. During its 1995–96 United States network television schedule, the series ranked 55th and was viewed by an average of 15.40 million viewers, an increase of almost seven percent over the second season, making it Foxs top-rated program in the 1849-year-old demographic.50}} Although the first three episodes of the fourth season aired on Friday night, the fourth episode "Unruhe" aired on Sunday night. The show remained on Sunday until its end.50}} The season hit a high with its twelfth episode, "Leonard Betts", which was chosen as the List of Super Bowl lead-out programs following Super Bowl XXXI. The episode was viewed by 29.1 million viewers, the series highest-rated episode. The fifth season debuted with "Redux I" on November 2, 1997 and was viewed by 27.34 million people, making it the highest-rated non-special broadcast episode of the series. The season ranked as the eleventh-most watched series during the 1997–98 United States network television schedule, with an average of 19.8 million viewers. It was the series highest-rated season as well as Fox highest-rated program during the 199798 season.
Question: Which two days did the series air during the fourth season?
Answer: Friday | Sunday