The mean GPA for students in School A is 3.0; the mean GPA for students in School B is 2.8. The standard deviation in both schools is 0.25. The GPAs of both schools are normally distributed. If 9 students are randomly sampled from each school, what is the probability that:

(a) the sample mean for School A will exceed that of School B by 0.5 or more?

(b) the sample mean for School B will be greater than the sample mean for School A?