Sarah is planning her study schedule for her upcoming exams. She plans to study 1.5 hours every weekday and 2 hours each on Saturday and Sunday. She has 3 weeks left until her exams. If she wants to study a total of 50 hours in these 3 weeks, how many additional hours will she need to study, if any, to meet her goal? Let's think step by step and output the final answer within \boxed{}.
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