ohai

The beta of the portfolio is not equal to 1 so the formulas will give different results but in 19.4 they specifically say hedging so i would always go with the Beta formula unless they specifically mention wanting to convert to a "synthetic cash" or synthetic equity portfolio.

My prob is that they have sometimes used the beta formula when talking about synthetic portfolios (either cash or equity) so in situations where i would use the Rf formula but the Q hasn't actually given the info needed to use the Rf so it's been one of those situations i mentioned before where you're forced into one of the formula