What is the name of the ship sunk by U-305 on 17 March 1943?
CREATE TABLE "allied_ships" (
  "date" text,
  "name" text,
  "flag" text,
  "tonnage_grt" real,
  "sunk_by" text
);
SELECT "name" FROM "allied_ships" WHERE "date"='17 march 1943' AND "sunk_by"='u-305';