when did the institution at chapel hill, North carolina join acc?
CREATE TABLE "member_schools" (
  "institution" text,
  "nickname" text,
  "location" text,
  "founded" real,
  "joined_acc" real,
  "school_type" text,
  "acc_football_titles" real
);
SELECT "joined_acc" FROM "member_schools" WHERE "location"='Chapel Hill, North Carolina';