Problem:
Assume that the % expected return for security A and the market M for a good, normal and bad economy (probabilities .3,.4,.3) are 20, 16, and 10 for A and 8, 4, and 12 for M. Also assume that you invest 40% in A and 60% in M.
Required:
Question: Compute the standard deviation for M.
Note: Please show how to work it out.