R 41 - Forwards and Future, Practice Problem 4 B

In the solution for Q4 B. the returns on the stock and bond have been considered for the original level of Beta and MD. However, the question says that the portfolio manager has changed the Beta and MD of the portfolio. Hence, to compare should we not try to estimate the returns on portfolio by extrapolating based on modified Beta and MD in the following way:- Return on the stock portfolio = 1.20/1.15 * 5% Return on Bond portfolio = 8.25/6.75 *1.35% Please help!