Which year was the vessel Deva built as a Panamax DNV class ship?
CREATE TABLE "fleet" (
  "vessel_name" text,
  "type" text,
  "built" real,
  "class" text,
  "flag" text
);
SELECT SUM("built") FROM "fleet" WHERE "class"='dnv' AND "type"='panamax' AND "vessel_name"='deva';