If a set of grades on a statistics examination is approximately normally distributed with mean of 74 and a standard deviation of 7.9, find
a) the lowest passing grade if the lowest 10% of the students are given 1.0?
b) the highest grade if the top 5% of the students are given 4.0?
c)the lowest grade if the top 10% of the students are given 4.0 and the next 25% are given 3.5?