def type_of_user(datum, city):
    """
    Takes as input a dictionary containing info about a single trip (datum) and
    its origin city (city) and returns the type of system user that made the
    trip.
    
    Remember that Washington has different category names compared to Chicago
    and NYC. 
    """

    user_type = ""
    # 'usertype'(Subscriber or Customer) or 'Member Type'(Registered or Casual)
    if city is "Washington":
        user_type = "Subscriber" if datum.get("Member Type") == "Registered" else "Customer"
    else:
        user_type = datum.get("usertype")

    return user_type