CREATE TABLE table_31378 ("Result" TEXT, "Date" TEXT, "Race" TEXT, "Venue" TEXT, "Group" TEXT, "Distance" TEXT, "Weight  ( kg ) " TEXT, "Jockey" TEXT, "Winner/2nd" TEXT)

What is the autumn classic weight?
SELECT "Weight (kg)" FROM table_31378 WHERE "Race" = 'Autumn Classic'
SELECT "Weight (kg)" FROM "table_31378" WHERE "Race" = 'Autumn Classic'