A marathon race covers a distance of 42 kilometers. If a runner maintains a constant speed of 10 kilometers per hour, how much time does it take for the runner to complete the marathon? After the marathon, the runner drinks water at a rate of 0.5 liters every 15 minutes for the next hour. How many liters of water does the runner drink in total during this time? Let's think step by step and output the final answer within \boxed{}.
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