What Surface has a Date of 15 february 1988?
CREATE TABLE "singles_5_3_2" (
  "outcome" text,
  "date" text,
  "championship" text,
  "surface" text,
  "opponent_in_the_final" text,
  "score_in_the_final" text
);
SELECT "surface" FROM "singles_5_3_2" WHERE "date"='15 february 1988';