可以说下这题用到的对冲的知识吗

问题如下：

How does adding leverage (borrowing at a risk-free rate, which is not random) to a portfolio change the optimal hedge ratio? For example, if the portfolio returns were doubled so that $\widetilde R_p = 2R_p$, what is the optimal hedge ratio for the Rp? Hint: Use the formula for the OLS estimator of $\beta$.

选项：

解释：

The OLS $\beta$ is $\frac{Cov(R_p, R_h)}{Var(R_h)}$. Scaling $R_p$ by a leverage v, the optimal hedge would be $\frac{Cov(vR_p, R_h)}{Var(R_h)} = v\frac{Cov(R_p, R_h)}{Var(R_h)}=v\beta$, where $\beta$ is the ledge ratio from the unlevered portfolio.

Levering up increases exposure to risk that can be hedged and to the hedge ratio must account for this.