Suppose that x is a random variable with mean 30 and standard deviation 4. Also suppose that y is a random variable with mean 50 and standard deviation 8. Assume that correlation between x and y is zero. Find the variance and standard deviation of the random variable z for each of the following cases.
a) Z = 35 – 10X
b) Z = 12X – 5
c) Z = X + Y
d) Z = X – Y
e) Z = -2X + 2Y





