What is the average goals when the last appearance was before 1984, there were more than 17 appearances, the first appearance was before 1961 and the position was mf?
CREATE TABLE "list_of_players" (
  "position" text,
  "appearances" real,
  "goals" real,
  "first_appearance" real,
  "last_appearance" real
);
SELECT AVG("goals") FROM "list_of_players" WHERE "last_appearance"<1984 AND "appearances">17 AND "first_appearance"<1961 AND "position"='mf';