A college professor noted that the grades of his students in an introductory statistics class were normally distributed with a mean of 52.50 and a standard deviation of 9. If 67.64% of his students...

A college professor noted that the grades of his students in an introductory statistics class were normally distributed with a mean of 52.50 and a standard deviation of 9. If 67.64% of his students received grades of C or above, what is the minimum score of those students receiving a grade of at least a C?