user: Question: What circuit had an Ensign N180 as the winning car in round 5?
Columns: ['Round', 'Name', 'Circuit', 'Date', 'Winning driver', 'Winning car']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'International Gold Cup', 'Oulton Park', 'April 9', 'Tony Trimmer', 'Fittipaldi F8']
SQL:

assistant: SELECT "Circuit" FROM "Table" WHERE "Winning car" = 'Ensign N180' AND "Round" = 5.0;