How many  FA Trophy has a Player of mario walsh and a League larger than 17?
CREATE TABLE "top_scorers_in_order_of_league_goals" (
  "player" text,
  "club" text,
  "league" real,
  "fa_cup" real,
  "fa_trophy" real,
  "league_cup" real,
  "total" real
);
SELECT AVG("fa_trophy") FROM "top_scorers_in_order_of_league_goals" WHERE "player"='mario walsh' AND "league">17;