Question: How many members are there in the cooperative that partnered with Mesa Citrus Growers Association during 1920s?

Context paragraphs:
Auburndale Citrus Growers Association Packing House: Auburndale Citrus Growers Association Packing House

Garden State Wine Growers Association: The Garden State Wine Growers Association (GSWGA) is an industry trade association established as an advocate for New Jersey's wine grape growers, providing leadership on research and education programs, public policies, sustainable farming practices and trade policy to enhance the New Jersey wine grape growing business and communities.  The association sponsors multiple wine festivals each year.  Vintage North Jersey, a subsidiary of the Garden State Wine Growers Association, was founded in 2013.  Vintage North Jersey includes ten wineries in northwestern New Jersey, and received a $16,000 tourism grant from the state of New Jersey.

E. Thurman Gaskill: E. Thurman Gaskill (born April 4, 1935) was the Iowa State Senator from the 6th District and Assistant Majority Leader of the Iowa Senate.  Mr. Gaskill is a grain farmer and a director of Meta Financial Group, Incorporated (NASDAQ: CASH ), a bank holding company.  He served in the Iowa Senate 1997–2007.  He has also been a commissioner of both Iowa's Department of Economic Development and its Department of Natural Resources, president of Iowa Corn Growers Association, president of National Corn Growers Association, chairman of the United States Feed Grains Council, and held other agriculture positions.

Mesa Citrus Growers Association: The Mesa Citrus Growers Association is a citrus growers association located in Mesa, Arizona.  It was founded in the 1920s to take advantage of the growing citrus industry in the region.  During this time, it partnered with Sunkist Growers, Incorporated, in a building that operated until 2010.

Old South (orange juice): Old South is the name of a brand of frozen concentrated orange juice (FCOJ) sold in Canada since 1939.  It produces a number of different kinds of orange juice, as well as other fruit juices.  The brand used to be owned by the Pasco Beverage Company, a citrus growers' cooperative, but was bought by Louis Dreyfus Citrus, the third largest orange juice producer in the world, which is owned by the Louis Dreyfus Group.

American Corn Growers Association: The American Corn Growers Association (ACGA) is a commodity and advocacy association founded in 1987 which represents the interests of corn (maize) producers in the United States, where corn is used for human and animal food and to produce ethanol.  A rival group, the National Corn Growers Association, is seen as more closely aligned with the food processing industry.

Western Canadian Wheat Growers Association: The Western Canadian Wheat Growers Association (WCWGA) is a private lobbying company located in Saskatoon, Canada.  Founded in 1970 as the Palliser Wheat Growers Association, the WCWGA opposes the Canadian Wheat Board's marketing status and supports open market competition in sales of wheat and barley.

National Corn Growers Association: The National Corn Growers Association (NCGA) is an association that represents and advocates for the interests of corn growers in the United States.  It is distinct from the American Corn Growers Association, a competing organization set up in 1987.

Mission Citrus Growers Union Packing Shed: The Mission Citrus Growers Union Packing Shed in Mission, Texas, also known as Edinburg Citrus Association and as Growers Select Produce Packing Shed, is a historic packing house.  It was built in 1944.  It was listed on the National Register of Historic Places in 2002.

Sunkist Growers, Incorporated: Sunkist Growers, Incorporated is an American citrus growers' non-stock membership cooperative composed of 6,000 members from California and Arizona.  It is currently headquartered in the Valencia neighborhood of Santa Clarita, California.  Through 31 offices in the United States and Canada and four offices outside North America, its sales in 1991 totalled $956 million.  It is the largest fresh produce shipper in the United States, the most diversified citrus processing and marketing operation in the world, and one of California's largest landowners.

Supporting paragraphs: Mesa Citrus Growers Association Sunkist Growers, Incorporated
Answer: 6,000