I was flying from London to Sydney with no stop-overs. I left London at 2:20 p.m. Tuesday (London time) and arrived in Sydney at 6:40 p.m. Wednesday (Syndey time). How long was the flight if Sydney is 11 hours ahead of London?

The answer i get is 17 hours, but the answer book says 17 hours 20 minutes.

If you get 17 hours 20 minutes please show the solution.