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 I don't even know where to start.