What is the sum of the weeks that games occured on october 21, 1974 and less than 50,623 fans attended?
CREATE TABLE "schedule" (
  "week" real,
  "date" text,
  "opponent" text,
  "result" text,
  "venue" text,
  "attendance" real
);
SELECT SUM("week") FROM "schedule" WHERE "date"='october 21, 1974' AND "attendance"<'50,623';