what is the maximum completed for delta bessborough
CREATE TABLE "buildings_completed_as_of_february_2011" (
  "rank" real,
  "building" text,
  "address" text,
  "height" text,
  "storeys" real,
  "completed" real
);
SELECT MAX("completed") FROM "buildings_completed_as_of_february_2011" WHERE "building"='Delta Bessborough';