user: Question: How many episodes had a production code of 5M13?
Columns: ['Ep.', 'Season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Prod. Code']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [52.0, 1.0, '"Initiation"', 'Michael Zinberg', 'Frank Dungan & Jeff Stein & Tony Sheehan', 'October 30, 1987', '5M03']
SQL:

assistant: SELECT COUNT("Ep.") FROM "Table" WHERE "Prod. Code" = '5M13';