What is the Tonnage that has builder AG Vulcan, and the original operator NDL, and the ship, Prinzess Irene?
CREATE TABLE "the_ships" (
  "ship" text,
  "tonnage" text,
  "builder" text,
  "original_operator" text,
  "fate" text
);
SELECT "tonnage" FROM "the_ships" WHERE "builder"='ag vulcan' AND "original_operator"='ndl' AND "ship"='prinzess irene';