4.72 Find some variances and standard deviations. 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...

I need some help with my stats homework. This comes from the textbook introduction to the practices of statistics ninth edition. Can you help me please. Only do (d)

Extracted text: 4.72 Find some variances and standard deviations. 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 the correlation between X and Y is zero. Find the vari- ance and the standard deviation of the random variable Z for each of the following cases. Be sure to show your work. (a) Z = 35 – 10X. (b) Z = 12X - 5. %3D


Extracted text: (c) Z = X + Y. (d) Z = X – Y. (e) Z = -2X + 2Y.