user: Question: List all directors when Brad Radnitz was the writer?
Columns: ['Episode #', 'Season #', 'Title', 'Directed by', 'Written by', 'Original airdate', 'Production code #']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'real']
Sample row: [50.0, 301.0, '"Ghost Town U.S.A."', 'Oscar Rudolph', 'Howard Leeds', 'September17,1971', 49.0]
SQL:

assistant: SELECT "Directed by" FROM "Table" WHERE "Written by" = 'Brad Radnitz';