On what surface was the match played with a score of 2–6, 6–3, 6–4?
CREATE TABLE "runner_up_16" (
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent_in_the_final" text,
  "score" text
);
SELECT "surface" FROM "runner_up_16" WHERE "score"='2–6, 6–3, 6–4';