user: Question: Name the number in the series for when the viewers is 7.78
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (millions)']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['29', '1', '" Gay Witch Hunt "', 'Ken Kwapis', 'Greg Daniels', 'September21,2006', '3001', '9.11']
SQL:

assistant: SELECT "No. in series" FROM "Table" WHERE "U.S. viewers (millions)" = '7.78';