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Ms. Chen, a teacher, explored the relationship between students’ study time (in hours per week) and their test scores (out of 100). She collected data from her class, where \(x\) represents the study hours per week and \(y\) represents the test score. After analysis, she derived the best-fit line equation: \(y = 4.2x + 55.6\). Using this equation, estimate the test score for a student who studies 8.5 hours per week.