On 1 september 2007, at the Venue A, what was the average attendance?
CREATE TABLE "irn_bru_second_division" (
  "date" text,
  "opponent" text,
  "venue" text,
  "result" text,
  "attendance" real
);
SELECT AVG("attendance") FROM "irn_bru_second_division" WHERE "venue"='a' AND "date"='1 september 2007';