On interchanging two digits of the number 2643, it decreased by 180. Which two digits of 2643 might have been interchanged? (a) 2 and 6 (b) 4 and 3 c) 6 and 3 (d) 6 and 4

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”?