CREATE TABLE table_68780 ("Tie no" TEXT, "Home team" TEXT, "Score" TEXT, "Away team" TEXT, "Attendance" TEXT)

What is the Tie no listed for the Away team of Barnet?
SELECT "Tie no" FROM table_68780 WHERE "Away team" = 'barnet'
SELECT "Tie no" FROM "table_68780" WHERE "Away team" = 'barnet'