user: Question: What is the cable rank for bbc three weekly ranking of N/A?
Columns: ['Episode no.', 'Airdate', 'Viewers', 'BBC Three weekly ranking', 'Cable rank']
Types: ['real', 'text', 'real', 'text', 'text']
Sample row: [1.0, '22 October 2009', 492000.0, 'N/A', 'N/A']
SQL:

assistant: SELECT "Cable rank" FROM "Table" WHERE "BBC Three weekly ranking" = 'N/A';