Scores on the SAT form a normal distribution with u=500 and o=100.

a. You are trying to qualify for a scholarship and find out that you need to have a higher score than at least 75% of the students. What score will you need?
b. What is the minimum score necessary to be in the top 15% of the SAT distribution?

Please show me how to work these problems.

I came up with a) 559.87 but I don't think I did it correctly (0.5987 *100+500). I can't even figure b.