What is the highest rank for a 6:52.70 time and notes of sa/b?
CREATE TABLE "quarterfinal_3" (
  "rank" real,
  "athlete" text,
  "country" text,
  "time" text,
  "notes" text
);
SELECT MAX("rank") FROM "quarterfinal_3" WHERE "notes"='sa/b' AND "time"='6:52.70';