What is the date where the tonnage is larger than 5,754 and the ship was sunk by U-305?
CREATE TABLE "allied_ships" (
  "date" text,
  "name" text,
  "flag" text,
  "tonnage_grt" real,
  "sunk_by" text
);
SELECT "date" FROM "allied_ships" WHERE "tonnage_grt">'5,754' AND "sunk_by"='u-305';