Table schema:
CREATE TABLE table_name_83 (tonnage___grt__ INTEGER, deaths VARCHAR, date VARCHAR, fate VARCHAR, flag VARCHAR)

Question: How much tonnage has a Fate of sunk, and a Flag of great britain, and a Date of 26 september 1940, and Deaths of 2?
SQL: SELECT SUM(tonnage___grt__) FROM table_name_83 WHERE fate = "sunk" AND flag = "great britain" AND date = "26 september 1940" AND deaths = 2