A cell phone company charges a monthly rate of $55 for unlimited text and data and $0.50 per minute for phone calls. The bill for last month was $66.

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”?