18. PLZ HELP For each part below, use the figure to fill in the blank. If necessary, you may learn what the markings on a figure indicate (a) Find AB (b) Find M< F (picture)​

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”?