John jogs at a speed of 4 miles per hour when he runs alone, but runs at 6 miles per hour when he is being dragged by his 100-pound German Shepherd dog. If John and his dog go on a run together for 30 minutes, and then John runs for an additional 30 minutes by himself, how far will John have traveled?
Please reason step by step, and put your final answer within \boxed{}.
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