Answer:
20.1%
Step-by-step explanation:
In capital asset prcing model (CAPM), cost of equity (or cost of retained earnings in this context) is calculated as below:
Cost of equity = risk-free rate of return + beta x (market index return - risk-free rate of return)
Please note that (market index return - risk-free rate of return) is equal to market risk premium
Putting all the number together, we have:
Cost of equity/retained earnings = 2.5% + 2.2 x 8% = 20.1%
Note: The dividend growth rate, tax rate & stock standard deviation is not relevant in answering the question.