CREATE TABLE table_65191 ("Rank" FLOAT, "Athlete" TEXT, "Country" TEXT, "Time" TEXT, "Notes" TEXT)

Which Rank has Notes of fb, and a Time of 5:57.31?
SELECT "Rank" FROM table_65191 WHERE "Notes" = 'fb' AND "Time" = '5:57.31'
SELECT "Rank" FROM "table_65191" WHERE "Notes" = 'fb' AND "Time" = '5:57.31'