What is the winning score of the tournament on 16 May 1993?
CREATE TABLE "lpga_tour_20" (
  "date" text,
  "tournament" text,
  "winning_score" text,
  "margin_of_victory" text,
  "runner_s_up" text
);
SELECT "winning_score" FROM "lpga_tour_20" WHERE "date"='16 may 1993';