Find the variance. part a. I would like to ask how to find the deviation is this questions? the cuircled part. thank you.

Portfolio Returns and Deviations Consider the following information on three stocks: a. If your portfolio is invested 25 percent each in A and B and 50 percent in C, what is the portfolio expected return? The variance? The standard deviation? b. If the expected T-bill rate is 4.10 percent, what is the expected risk premium on the portfolio? c. If the expected inflation rate is 3.50 percent, what are the approximate and exact expected real returns on the portfolio? What are the approximate and exact expected real risk premiums on the portfolio? P2=.25(.3975.1230)2+.25(.0825).1230)2+.50(.2775).1230)2 2p=.04757 P=.047571/2 P=.2181, or 21.81% why? How to get there - revered