Part C答案中
A mean-variance improvement would be achieved if the Sharpe ratio for non-domestic
developed market equity is greater than the product of the Sharpe ratio of the current endowment
portfolio and its correlation to non-domestic developed market equity.
为何要用non-domestic Sharpe Ration和组合Sharpe ratio 乘以non-domestic与组合的correlation进行比较，讲义中并未看到此方法。
同时，Part D中关于conditional return correlation的描述并未在讲义中找到，是因为教材改版的原因吗？
