What is the lowest round with a place of t15 in a year earlier than 1998?
CREATE TABLE "tournaments" (
  "year" real,
  "tournament" text,
  "round_1" real,
  "round_2" real,
  "round_3" real,
  "round_4" real,
  "score" real,
  "to_par" text,
  "place" text,
  "money" real
);
SELECT MIN("round_1") FROM "tournaments" WHERE "place"='t15' AND "year"<1998;