user: Question: How many people wrote the episode directed by Arvin Brown?
Columns: ['Series #', 'Title', 'Directed by', 'Written by', 'Original air date', 'Viewers (million)']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '"Pilot"', 'Mikael Salomon', 'John Masius', 'June16,2009', '3.82']
SQL:

assistant: SELECT COUNT("Written by") FROM "Table" WHERE "Directed by" = 'Arvin Brown';