✔ 最佳答案
If you are familiar with the Security Market Line (SML) used in the Capital Asset Pricing Model (CAPM), you know that the risk free rate plots ON the y-intercept at a beta of 0. Since the market beta is 1, you want to weight your portfolio such that...
(weight of risk free asset x 0) + (weight of stock X * stock X ß) = 1
reducing the above equation...
[where w = weight]
wX * ßX = 1
so...
1 / ßX = wX
1 / 1.68 = 0.59524, or 59.524% should be in stock X,
with the remainder ( 1 - 0.59524) = 0.40476, or 40.476% in the risk free asset (Tbill)
Thus your Portfolio beta = market beta = 1
(wRiskFree * ßRiskFree) + (wX * ßX) = 1
[(0.40476 * 0) + (0.59524 * 1.68) = 1