Which Surface has an Opponent in the final of don mcneill, and a Year of 1940?
CREATE TABLE "grand_slam" (
  "outcome" text,
  "year" real,
  "championship" text,
  "surface" text,
  "opponent_in_the_final" text,
  "score_in_the_final" text
);
SELECT "surface" FROM "grand_slam" WHERE "opponent_in_the_final"='don mcneill' AND "year"=1940;