What is the average goal difference using slavia sofia club?
CREATE TABLE table_33105 (
    "Position" real,
    "Club" text,
    "Played" real,
    "Wins" real,
    "Draws" real,
    "Losses" real,
    "Goals for" real,
    "Goals against" real,
    "Points" real,
    "Goal Difference" real
)
SELECT AVG("Goal Difference") FROM table_33105 WHERE "Club" = 'slavia sofia'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the average goal difference using slavia sofia club? ### Input: CREATE TABLE table_33105 (
    "Position" real,
    "Club" text,
    "Played" real,
    "Wins" real,
    "Draws" real,
    "Losses" real,
    "Goals for" real,
    "Goals against" real,
    "Points" real,
    "Goal Difference" real
) ### Response: SELECT AVG("Goal Difference") FROM table_33105 WHERE "Club" = 'slavia sofia'