A delivery truck travels 50 miles at an average speed of 25 miles per hour. Then, it travels an additional 100 miles at an average speed of 50 miles per hour. Finally, it travels another 50 miles at an average speed of 25 miles per hour. Calculate the total distance traveled and the total time taken for the journey. What is the truck’s average speed for the entire trip? Let's think step by step and output the final answer within \boxed{}.
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