Who made the challenge in the Australian Grand Prix?
CREATE TABLE "table1_25531112_2" (
  "rd" text,
  "event" text,
  "circuit" text,
  "city_state" text,
  "date" text,
  "championship" text,
  "challenge" text,
  "production" text
);
SELECT "challenge" FROM "table1_25531112_2" WHERE "event"='Australian Grand Prix';