user: Question: How many people wrote the episode with 3.40 million U.S viewers?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'U.S. viewers (in millions)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [19.0, 1.0, '" Summer, Kind of Wonderful "', 'J. Miller Tobin', 'Joshua Safran', 'September1,2008', '3.43']
SQL:

assistant: SELECT COUNT("Written by") FROM "Table" WHERE "U.S. viewers (in millions)" = '3.40';