What is the round when the prize money is £7,500?
CREATE TABLE "calendar" (
  "round" text,
  "main_date" text,
  "number_of_fixtures" real,
  "clubs" text,
  "new_entries_this_round" text,
  "prize_money" text,
  "player_of_the_round" text
);
SELECT "round" FROM "calendar" WHERE "prize_money"='£7,500';