What is the Week when the winner was mary joe fernández 6–4, 7–5?
CREATE TABLE "october" (
  "week_of" text,
  "tier" text,
  "winner" text,
  "runner_up" text,
  "semi_finalists" text
);
SELECT "week_of" FROM "october" WHERE "winner"='mary joe fernández 6–4, 7–5';