Assuming a normal population distribution with a mean of 125 and a standard deviation of 25, what is the probability of obtaining the following means for groups of subjects chosen by random sampling?
a. Sample mean = 130 or higher, N = 25
b. Sample mean = 130 or higher, N = 81
c. Sample mean = 130 or lower, N = 81
d. Sample mean = 120 or higher, N = 36
e. Sample mean = 120 or lower, N = 49