Please reason step by step, and put your final answer within \boxed{}.
Harry started a 7-mile hike with a full 9-cup canteen of water and finished the hike in 2 hours with 3 cups of water remaining in the canteen. The canteen leaked at a certain rate per hour and Harry drank 2 cups of water during the last mile. He drank 0.6666666666666666 cups per mile during the first 6 miles of the hike. What was the rate at which the canteen leaked per hour?
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