Answer:
Portfolio A and Portfolio B
Explanation:
In this question, we apply the Capital Asset Pricing Model (CAPM) formula which is shown below
Expected rate of return = Risk-free rate of return + Beta × (Market rate of return - Risk-free rate of return)
The Market rate of return - Risk-free rate of return) = Market risk premium
Let us assume the market risk premium be X
For Portfolio A:
21% = 8% + 1.3 × X
13% = 1.3 × X
So, the X = 10%
For Portfolio B:
17% = 8% + 0.7 × X
9% = 0.7 × X
So, the X = 12.86%
Based on the market risk premium calculations, we can conclude that Portfolio A should be in short position while Portfolio B should be in long position as portfolio B has higher market risk premium than B