How many opponents were there at the game with 64,087 people in attendance?
CREATE TABLE "schedule" (
  "week" text,
  "date" text,
  "opponent" text,
  "result" text,
  "kickoff_a" text,
  "game_site" text,
  "tv" text,
  "attendance" text,
  "record" text
);
SELECT COUNT("opponent") FROM "schedule" WHERE "attendance"='64,087';