What is the larges week for the date  august 9, 1968 and less than 64,020 in attendance?
CREATE TABLE "exhibition_schedule" (
  "week" real,
  "date" text,
  "opponent" text,
  "result" text,
  "attendance" real
);
SELECT MAX("week") FROM "exhibition_schedule" WHERE "date"='august 9, 1968' AND "attendance"<'64,020';