Context_1 : The 668th Aircraft Control and Warning Squadron is an inactive United States Air Force unit. It was last assigned to the San Francisco Air Defense Sector, Air Defense Command, stationed at Mather Air Force Base, California. It was inactivated on 1 September 1961. Context_2 : The 920th Aircraft Control and Warning Squadron is an inactive United States Air Force unit. It was last assigned to the Goose Air Defense Sector, Air Defense Command, stationed at Resolution Island Air Station, Northern Territories, Canada. It was inactivated on 1 November 1961. Context_3 : The 926th Aircraft Control and Warning Squadron is an inactive United States Air Force unit. It was last assigned to the Goose Air Defense Sector, Air Defense Command, stationed at Frobisher Bay Air Base, Northwest Territories, Canada. It was inactivated on 1 November 1961. Context_4 : The 912th Aircraft Control and Warning Squadron is an inactive United States Air Force unit. It was last assigned to the Sault Sainte Marie Air Defense Sector, Air Defense Command, stationed at Ramore Air Station, Ontario, Canada. It was inactivated on 1 January 1962. Context_5 : The 128th Air Control Squadron (ACS) is one of the units of the Wisconsin Air National Guard based at Volk Field Air National Guard Base, located in Camp Douglas, WI. Originally established as the 128th Aircraft Control and Warning Squadron in 1947 at General Billy Mitchell Field, it was subsequently re-designated as a Control and Reporting Post, and a Forward Air Control Post-Heavy. In October 1991, the unit was transferred to its current base as the 128 Air Control Squadron. Context_6 : The 677th Aircraft Control and Warning Squadron is an inactive United States Air Force unit. It was last assigned to the 30th Air Division, Air Defense Command, stationed at Alpena Air Force Station, Michigan. It was inactivated on 30 November 1957. Context_7 : Mather Air Force Base (Mather AFB) was a United States Air Force Base, which was closed in 1993. It was located 12 mi east of Sacramento, on the south side of U.S. Route 50 in Sacramento County, California. Mather Field was one of 32 Air Service training camps established after the United States entry into World War I in April 1917. Context_8 : The 812th Aircraft Control and Warning Squadron is an inactive United States Air Force unit. It was last assigned to the Oklahoma City Air Defense Sector, Air Defense Command, stationed at Lake Charles Air Force Station, Oklahoma. It was discontinued on 1 September 1961. Context_9 : The 915th Aircraft Control and Warning Squadron is an inactive United States Air Force unit. It was last assigned to the Duluth Air Defense Sector, Air Defense Command, stationed at Sioux Lookout Air Station, Ontario, Canada. It was inactivated on 1 October 1962. Context_10 : The 740th Aircraft Control and Warning Squadron AKA 740th AC&W Squadron is an inactive United States Air Force unit. It was last assigned to the Minot Air Defense Sector, Aerospace Defense Command, stationed at Ellsworth Air Force Base, South Dakota. It was discontinued on 15 August 1962. fact_1 :  It was last assigned to the San Francisco Air Defense Sector, Air Defense Command, stationed at Mather Air Force Base, California. fact_2 : Mather Air Force Base (Mather AFB) was a United States Air Force Base, which was closed in 1993. Question: Where was the 668th Aircraft Control and Warning Squadron last stationed at?
Output: Mather Air Force Base