Alex (Adelaide, Australia), Gerda (Gelsenkirchen, Germany) and Craig (Calgary, Canada) want to talk using Skype videoconference.
Adelaide time is GMT +10:30; the local time is 10:30 ahead of the Greenwich Mean Time (GMT or the UK time).
Gelsenkirchen time is GMT +1:00.
Calgary time is GMT -7:00.
How much time between 9:00 and 23:00 local time do they have for a conversation among all three together?