user: Question: Name the total number of years for chassis of ensign n175
Columns: ['Year', 'Entrant', 'Chassis', 'Engine', 'Points']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1978.0, 'Mario Deliotti Racing', 'Ensign N175', 'Ford V8', 0.0]
SQL:

assistant: SELECT COUNT("Year") FROM "Table" WHERE "Chassis" = 'ensign n175';