How many characters were portrayed by the informant of don flack?
CREATE TABLE "table1_11240028_3" (
  "character" text,
  "portrayed_by" text,
  "relationship" text,
  "first_appearance" text,
  "last_appearance" text
);
SELECT COUNT("portrayed_by") FROM "table1_11240028_3" WHERE "relationship"='Informant of Don Flack';