Question: Brian Olsen was the last WEC Champion before it was purchased by which sports promotion company?

full_context: Document 1: Frank Fertitta III: Frank Joseph Fertitta III (born February 24, 1962) is an American entrepreneur. He is the current CEO of Station Casinos. He is also an owner of Zuffa LLC, which is the entity that formerly ran the Ultimate Fighting Championship (UFC).
Document 2: Brian Olsen: Brian Olsen (born 1975) is an American former mixed martial artist who fought mainly in World Extreme Cagefighting. He was the last WEC Heavyweight Champion before it was abolished when Zuffa purchased the organization.
Document 3: Zuffa: Zuffa, LLC ( ) is an American sports promotion company specializing in mixed martial arts. It was founded in January 2001 in Las Vegas, Nevada, by Station Casinos executives Frank Fertitta III and Lorenzo Fertitta to be the parent entity of the Ultimate Fighting Championship (UFC) after they purchased it from the Semaphore Entertainment Group. The word "Zuffa" is an Italian word (] ), meaning "fight". On July 11, 2016, Zuffa announced that it would be purchased by WME-IMG for the price of $4 billion.
Document 4: Brian Camozzi: Brian "The Mantis" Camozzi (born June 24, 1991) is an American mixed martial artist. He was the Welterweight Champion for Resurrection Fighting Alliance and Sparta Combat League. Camozzi currently fights in Welterweight division in the Ultimate Fighting Championship (UFC). He is the younger brother of former UFC Middleweight fighter Chris Camozzi.
Document 5: List of Irish UFC fighters: The Ultimate Fighting Championship (UFC) is a mixed martial arts (MMA) promotion, founded in 1993 by Art Davie and Rorion Gracie. The organization was purchased from its parent company SEG in 2001 by Zuffa LLC, a promotional company owned by Las Vegas casino magnates, Lorenzo and Frank Fertitta and managed by Dana White (current president of operations). Since its inception, and through its current Zuffa management, the UFC has remained one of the more dominant MMA promotions in the world, playing host to a wide field of MMA fighters.
Document 6: Dan Henderson: Daniel Jeffery Henderson (born August 24, 1970) is an American former mixed martial artist and Olympic wrestler, who last competed as a middleweight in the Ultimate Fighting Championship. He was the last Strikeforce Light Heavyweight Champion and was the last Welterweight (80 kg ) and Middleweight (95 kg ) champion of Pride Fighting Championships. Additionally, Henderson was the Brazil Open '97 Tournament Champion, the UFC 17 Middleweight Tournament Champion, the Rings: King of Kings 1999 Tournament Champion and the Pride Weltwerweight Grand Prix Tournament Champion. During his career, Henderson also challenged for the UFC Middleweight Championship (2x), the UFC Light Heavyweight Championship and the Strikeforce Middleweight Championship. He was the first mixed martial artist to concurrently hold two titles in two different weight classes in a major MMA promotion. At the time of his retirement after UFC 204, he was the oldest fighter on the UFC roster. Known to be one of the greatest mixed martial artists of all time having defeated a total of seventeen MMA world champions across four major MMA promotions (UFC, PRIDE FC, Strikeforce, and RINGS).
Document 7: UFC 30: UFC 30: Battle on the Boardwalk was a mixed martial arts event held by the Ultimate Fighting Championship at the Trump Taj Mahal in Atlantic City, New Jersey on February 23, 2001. UFC 30 was the first UFC event under the new ownership of Zuffa, LLC, and also the first UFC event since UFC 22 to see a home video release.
Document 8: Ultimate Fighting Championship: The Ultimate Fighting Championship (UFC) is an American mixed martial arts organization based in Las Vegas, Nevada, that is owned and operated by parent company WME–IMG. It is the largest MMA promotion in the world and features the top-ranked fighters of the sport. Based in the United States, the UFC produces events worldwide that showcase eleven weight divisions and abide by the Unified Rules of Mixed Martial Arts. As of 2017, the UFC has held over 400 events. Dana White serves as the president of the UFC. He has held that position since 2001; while under the leadership of Dana White the UFC has grown into a globally popular multibillion-dollar enterprise.
Document 9: Ken Pavia: Ken Pavia is a former sports agent, founder of the Huntington Beach, California based sports agency MMAagents and the former CEO of India’s first MMA Promotion Super Fight League. From 2005 to September 2011 Pavia represented a client roster of 75 professional mixed martial artists at MMAagents, most of whom competed in top tier mixed martial arts promotions such as the Ultimate Fighting Championship (UFC), World Extreme Cagefighting (WEC), Pride Fighting Championships, Strikeforce, DREAM, and Bellator Fighting Championship.
Document 10: Chris Leben: Christian Cyrus Leben (born July 21, 1980) is a retired American mixed martial artist. He formerly competed with the UFC as a Middleweight, compiling a record of 12-10 in 22 appearances for the organization. Leben first appeared in the inaugural season of "The Ultimate Fighter" reality series, and has also fought in the now-defunct WEC. He began his UFC career with five victories in a row before suffering a knockout loss to future UFC Middleweight Champion Anderson Silva. Leben was the inaugural WEC Middleweight Champion.
Document 11: Ben Askren: Ben Askren (born July 18, 1984) is an American former amateur wrestler for the University of Missouri and U.S. Olympic team. He is now an active submission wrestler, mixed martial artist, and the former Bellator Welterweight Champion and the current ONE Welterweight Champion known for his unorthodox and effective wrestling. He is currently ranked as the #7 welterweight in the world by Fight!Magazine and as the #10 welterweight by Sherdog.
Document 12: World Extreme Cagefighting: World Extreme Cagefighting (WEC) was an American mixed martial arts (MMA) promotion founded in 2001. It was purchased by Zuffa, LLC, the parent company of the Ultimate Fighting Championship (UFC), in 2006. In its final incarnation, it was made up of 3 weight classes: 135 lb , 145 lb and 155 lb . To accommodate the smaller fighters, WEC's cage was 25 feet in diameter—5 feet smaller than the standard UFC cage.
Document 13: WEC 20: WEC 20: Cinco de Mayhem was a mixed martial arts event held by World Extreme Cagefighting that took place on May 5, 2006 at Tachi Palace Hotel & Casino in Lemoore, California. "WEC 20"'s main event was a heavyweight bout between Brian Olsen and Mike Kyle.
Document 14: List of current UFC fighters: The Ultimate Fighting Championship (UFC) is a mixed martial arts (MMA) promotion, founded in 1993 by Art Davie and Rorion Gracie. The organization was purchased from its parent company SEG in 2001 by Zuffa LLC, a promotional company owned by Las Vegas casino magnates, Lorenzo Fertitta and Frank Fertitta and managed by Dana White (current president of operations). In 2016, it was sold to Christoffer Ahl (WME-IMG) for $4 billion. Since its inception, and through its Zuffa management, the UFC has remained one of the more dominant MMA promotions in the world, playing host to a wide field of MMA fighters.
Document 15: Sean Sherk: Sean Keith Sherk (born August 5, 1973) is a retired American mixed martial artist and former UFC Lightweight Champion. Sherk competed in the Ultimate Fighting Championship and was one of the first combatants to have been a championship competitor in multiple weight divisions (having also competed for the UFC Welterweight Championship). He was the second UFC Lightweight Champion in the organization's history after Jens Pulver vacated his title 5 years earlier. Sherk also spent time competing in the Japan-based organizations, PRIDE Fighting Championships and Pancrase; going undefeated in both promotions. He holds one of the longest undefeated streaks in mixed martial arts history, with only four career losses, all to fellow-UFC Champions. Sherk announced his official retirement from mixed martial arts competition in September 2013 having last fought three years prior.
ground_truth: Zuffa, LLC