What year was the brabham bt46 bt48 bt49 Chassis common?
CREATE TABLE table_name_89 (year INTEGER, chassis VARCHAR)
SELECT AVG(year) FROM table_name_89 WHERE chassis = "brabham bt46 bt48 bt49"
### Context: CREATE TABLE table_name_89 (year INTEGER, chassis VARCHAR) ### Question: What year was the brabham bt46 bt48 bt49 Chassis common? ### Answer: SELECT AVG(year) FROM table_name_89 WHERE chassis = "brabham bt46 bt48 bt49"