Suppose that X is a random variable with mean 20 and standard deviation 2. Also suppose that Y is a random variable with mean 40 and standard deviation 7. Assume that the correlation between X and Y is zero. Find the mean of the random variable Z for each of the following cases. Be sure to show your work.

A) Z=25−12X.
B) Z=13X−8.
C) Z=X+Y.
E) Z=X−Y.
E) Z=−3X+3Y.