user: Question: Name the number of writers for airdate of 15 July 1967
Columns: ['No', 'Season', 'Ep', 'Title', 'Writer', 'Director', 'Original airdate', 'Archive']
Types: ['real', 'real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [2.0, 1.0, 1.0, "'The Good Ones Are All Dead'", 'James Mitchell', 'Toby Robertson', '8 July 1967', 'Survives']
SQL:

assistant: SELECT COUNT("Writer") FROM "Table" WHERE "Original airdate" = '15 July 1967';