5. Given the relative-frequency table below, find the expected value of x. x P(X = x) 3 .02 5 .39 7 .12 9 .47

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?