I got 40/100 on a 5 question test, Geometry 10b could anyone help? My parents are super strict and it brought my grade from 82 down to a 75. Please add me or message me I REALLY need help!

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”?