A class of students took two exams. The first exam was worth 40% of their final grade, and the second exam was worth 60% of their final grade. If a student scored 70 on the first exam and needs an average final grade of at least 75 to pass the class, what is the minimum score the student must achieve on the second exam to pass? Let's think step by step and output the final answer within \boxed{}.
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