Which IHSAA Football Class has a County of 77 sullivan, and a School of union dugger?
CREATE TABLE "indiana_high_school_athletics_conference" (
  "school" text,
  "location" text,
  "mascot" text,
  "enrollment" real,
  "ihsaa_football_class" text,
  "county" text
);
SELECT "ihsaa_football_class" FROM "indiana_high_school_athletics_conference" WHERE "county"='77 sullivan' AND "school"='union dugger';