What is the average First Downs for december 4?
CREATE TABLE "schedule" (
  "week" real,
  "date" text,
  "result" text,
  "record" text,
  "opponent" text,
  "points_for" real,
  "points_against" real,
  "first_downs" real,
  "attendance" real
);
SELECT AVG("first_downs") FROM "schedule" WHERE "date"='december 4';