Math SAT Scores for Students Admitted to University a Are

Multiple Choice

Math SAT scores for students admitted to University A are bell-shaped with a mean of 520 and a standard deviation of 60. Math SAT scores for students admitted to University B are also bell-shaped, but with a mean of 580 and a standard deviation of 45. Suppose you plan to take a simple random sample of 15 students from University A and 25 students from University B. Let x_B-x_A be the difference in sample mean math SAT scores between the two samples (B - A) .
-If you were to take a very large number of samples, about how far away would you expect x_B-x_A to fall from its mean?

A) 24.49 points
B) 17.92 points
C) 12.61 points
D) 6.49 points