SELECT COUNT("Crowd") FROM table_11473 WHERE "Away team" = 'north melbourne'
When North Melbourne is the Away team, what is the total number of the Crowd?
CREATE TABLE table_11473 (
    "Home team" text,
    "Home team score" text,
    "Away team" text,
    "Away team score" text,
    "Venue" text,
    "Crowd" real,
    "Date" text
)