Among freshmen at a certain university scores on the math sat followed the normal curve

Among freshman at a certain university, scores on the Math SAT followed the normal curve, with an average of 550 and an SD of 100. Fill in the blanks; explain briefly.

a) A student who scored 400 on the Math SAT was at the ______ th percentile of the score distribution.
b) To be at the 75th percentile of the distribution, a student needed a score of about ______ points on the Math SAT.