user: Question: On what type of surface did they play on 13 February 1994?
Columns: ['Date', 'Tournament', 'Surface', 'Opponent in the final', 'Score']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['3 November 1991', 'Scottsdale , USA', 'Hard', 'Chanda Rubin', '7–5, 6–1']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Date" = '13 February 1994';