If a set of grades on a statistics examination are approximately normally distributed with a mean of 75 and a standard deviation of 8, find a)the lowest passing grade of the lowest 10% of the students...

If a set of grades on a statistics examination are approximately normally distributed with a mean of 75 and a standard deviation of 8, find

a)the lowest passing grade of the lowest 10% of the students are given F's.

b)the highest B if the top 5% of the students are given A's.

c)the lowest B if the top 10% are given A's and the next 25% are given B's.