what is the tonnage of the ship koningin juliana?
CREATE TABLE "ships_operated_by_zeeland_steamship_comp" (
  "ship_s_name" text,
  "date_entered_service" text,
  "date_withdrawn" text,
  "tonnage" real,
  "type_of_ship" text
);
SELECT "tonnage" FROM "ships_operated_by_zeeland_steamship_comp" WHERE "ship_s_name"='koningin juliana';