Singer Terhaar - GIM Sharpe not Given?

In the Singer Terhaar approach, do you use the risk free rate for the investor’s country to calculate global market Sharpe if it’s not given?

There’s a question in Schweser’s mock asking to calculate GIM Sharpe, where they only give the expected return and std dev of GIM, and the risk free rate of Australia which is considered to be fully integrated with the world market.

Exam 3 - Morning - Q10

For me, Singer-Terhaar is a fancy name for ICAPM, only risk premium is involved in any calculation from the equation.