user: Question: What is the sum of the episode numbers where Chip Esten is the 4th performer and Christopher Smith was the 2nd performer?
Columns: ['Date', 'Episode', 'Performer 1', 'Performer 2', 'Performer 3', 'Performer 4']
Types: ['text', 'real', 'text', 'text', 'text', 'text']
Sample row: ['24 January 1992', 1.0, 'Jim Sweeney', 'Steve Steen', 'Stephen Frost', 'Tony Slattery']
SQL:

assistant: SELECT SUM("Episode") FROM "Table" WHERE "Performer 4" = 'Chip Esten' AND "Performer 2" = 'Christopher Smith';