A research study found that for the new-coming medical students, the correlation between the trail Medical College Admission Test (MCAT) grades and...

A research study found that for the new-coming medical students, the correlation between the trail Medical College Admission Test (MCAT) grades and real MCAT grades was 0.60. The variance of pre-exam grades was 81 and the variance of post-exam grades was 100. Thus, the variance of the difference between pre-exam and post-exam grades is:  (show work)