In the spring of 1967, Mac Hack VI played in the Boston Amateur championship, winning two games and drawing two games. Mac Hack VI beat a 1510 United States Chess Federation player. This was the first time a computer won a game in a human tournament. At the end of 1968, Mac Hack VI achieved a rating of 1529. The average rating in the USCF was near 1500. In 1968, Northwestern University students Larry Atkin, David Slate and Keith Gorlen began work on Chess (Northwestern University). On 14 April 1970 an exhibition game was played against Australian Champion Fred Flatow, the program running on a Control Data Corporation 6600 model. Flatow won easily. On 25 July 1976, Chess 4.5 scored 5–0 in the Class B (1600–1799) section of the 4th Paul Masson chess tournament in Saratoga, California. This was the first time a computer won a human tournament. Chess 4.5 was rated 1722. Chess 4.5 running on a Control Data Corporation CDC Cyber 175 supercomputer (2.1 megaflops) looked at less than 1500 positions per second. On 20 February 1977, Chess 4.5 won the 84th Minnesota Open Championship with 5 wins and 1 loss. It defeated expert Charles Fenner rated 2016. On 30 April 1978, Chess 4.6 scored 5–0 at the Twin Cities Open in Minneapolis. Chess 4.6 was rated 2040. International Master Edward Lasker stated that year, "My contention that computers cannot play like a master, I retract. They play absolutely alarmingly. I know, because I have lost games to 4.7." For a long time in the 1970s and 1980s, it remained an open question whether any chess program would ever be able to defeat the expertise of top humans. In 1968, International Master David Levy made a famous bet that no chess computer would be able to beat him within ten years. He won his bet in 1978 by beating Chess 4.7 (the strongest computer at the time). In 1981, Cray Blitz scored 5–0 in the Mississippi State Championship. In round 4, it defeated Joe Sentef (2262) to become the first computer to beat a master in tournament play and the first computer to gain a master rating (2258). In 1988, HiTech won the Pennsylvania State Chess Championship with a score of 4½–½. HiTech defeated International Master Ed Formanek (2485). The Harvard Cup Man versus Computer Chess Challenge was organized by Harvard University.