user: Question: What year did Freddie Frith win the 350cc and Enrico Lorenzetti win the 500cc?
Columns: ['Year', 'Designated Grand Prix', 'Track', '250 cc', '350 cc', '500 cc', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1948', 'Ulster Grand Prix', 'Clady', 'Maurice Cann', 'Freddie Frith', 'Enrico Lorenzetti', 'Report']
SQL:

assistant: SELECT "Year" FROM "Table" WHERE "350 cc" = 'Freddie Frith' AND "500 cc" = 'Enrico Lorenzetti';