325 nm at 315 kts would take 1hr 2mins not 1hr 18 mins (325/315 x 60) so planned ETA would be 11:30 + 1:02 = 12:32. From Fix at 12:05 to B at 12:32 would be 160 nm (325 - 165) in 27 mins = 160/27 x 60 = 355 kts