What is the total Tonnage GRT with a Type of cargo ship, and a Nationality of norway?
CREATE TABLE "ships_sunk_or_captured_by_moewe_on_her_s" (
  "date" text,
  "ship" text,
  "type" text,
  "nationality" text,
  "tonnage_grt" real
);
SELECT SUM("tonnage_grt") FROM "ships_sunk_or_captured_by_moewe_on_her_s" WHERE "type"='cargo ship' AND "nationality"='norway';