user: Question: Name the total number of production code by David Richardson and Todd Holland
Columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '" Pilot "', 'Todd Holland', 'Linwood Boomer', 'January 9, 2000', '10012-99-179']
SQL:

assistant: SELECT COUNT("Production code") FROM "Table" WHERE "Written by" = 'David Richardson' AND "Directed by" = 'Todd Holland';