mean-variance utility function 公式和risk aversion coecient

(a) Determine the proportion of each asset class in the portfolio that max-

imizes your expected utility.

(b) Determine the proportion of each asset class in the portfolio that max-

imizes your expected utility if you're only allowed to invest in the risky funds.

(c) Draw the following on the same graph: The efficientt frontier, the

minimum-variance portfolio, the tangency portfolio, the portfolio found in 7a

and the portfolio found in 7b.

我的尝试解答：

第二问就不太会了，要怎么又optimal risky又能求u的最大值？是用Ec=0.2*ws+0.12*(1-ws)这个式子算嘛？如果全部投risk的话，risk free的部分是0吗？