Schema: CREATE TABLE table_name_90 (assists VARCHAR, opponent VARCHAR, team VARCHAR, competition VARCHAR, total_gs VARCHAR)
Question: How many assists were in the k-league competition, which has more than 20 total Gs, the pohang steelers team, and chunnam dragons as the opponent?
SQL: SELECT assists FROM table_name_90 WHERE competition = "k-league" AND total_gs > 20 AND team = "pohang steelers" AND opponent = "chunnam dragons"