user: Question: What is the lowest round with a place of t15 in a year earlier than 1998?
Columns: ['Year', 'Tournament', 'Round 1', 'Round 2', 'Round 3', 'Round 4', 'Score', 'To par', 'Place', 'Money (￥)']
Types: ['real', 'text', 'real', 'real', 'real', 'real', 'real', 'text', 'text', 'real']
Sample row: [1998.0, 'Casio World Open', 69.0, 74.0, 71.0, 70.0, 284.0, '−4', 'T15', 1602000.0]
SQL:

assistant: SELECT MIN("Round 1") FROM "Table" WHERE "Place" = 't15' AND "Year" < 1998.0;