CREATE TABLE table_30728 ("Institution" TEXT, "Nickname" TEXT, "Location" TEXT, "Founded" FLOAT, "Joined ACC" FLOAT, "School Type" TEXT, "ACC Football Titles" FLOAT)

what year did north carolina institution join the acc?
SELECT MAX("Joined ACC") FROM table_30728 WHERE "Institution" = 'North Carolina'
SELECT MAX("Joined ACC") FROM "table_30728" WHERE "Institution" = 'North Carolina'