user: Question: What was the first airdate with a viewership of 4.77 million?
Columns: ['Episode', 'Original title', 'Directed by', 'Written by', 'Original airdate', 'Duration', 'Viewership']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [8.0, '" Testing Times "', 'Dewi Humphreys', 'Jim Sullivan', '15September2006', '30 minutes', '5.04 million']
SQL:

assistant: SELECT "Original airdate" FROM "Table" WHERE "Viewership" = '4.77 million';