What outcome has yvonne vermaak as the opponent?
CREATE TABLE "singles_6_2_titles_4_runners_up" (
  "outcome" text,
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent" text,
  "score" text
);
SELECT "outcome" FROM "singles_6_2_titles_4_runners_up" WHERE "opponent"='yvonne vermaak';