user: Question: What was the court surface when the score was 6–4, 6–1?
Columns: ['Date', 'Tournament', 'Surface', 'Opponent in the final', 'Score']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['21 October 2002', 'Windhoek', 'Hard', 'Gwinyai Tongoona', '7–5, 6–1']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Score" = '6–4, 6–1';