user: Question: who were the writers of the episode that had 5.56 millions of north american viewers? 
Columns: ['Series #', 'Season #', 'Title', 'Written by', 'Original air date', 'U.S. viewers (millions)']
Types: ['real', 'real', 'text', 'text', 'text', 'text']
Sample row: [68.0, 1.0, '"Bahamian Rhapsody"(Part 2)', 'Kari Lizer & Jeff Astrof', 'September23,2009', '7.17']
SQL:

assistant: SELECT "Written by" FROM "Table" WHERE "U.S. viewers (millions)" = '5.56';