user: Question: What was the constructor for round 15?
Columns: ['Rnd', 'Race', 'Date', 'Location', 'Pole Position', 'Fastest Lap', 'Race Winner', 'Constructor', 'Report']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Argentine Grand Prix', '9 January', 'Buenos Aires', 'James Hunt', 'James Hunt', 'Jody Scheckter', 'Wolf - Ford', 'Report']
SQL:

assistant: SELECT "Constructor" FROM "Table" WHERE "Rnd" = 15.0;