You have a portfolio that is invested 25% in the risk-free asset, 25% in a market index fund, 25% in a stock with a beta of 0.83, and 25% in a stock with a beta of 1.38. If the risk-free rate is 3% and the market risk premium is 13%, what is the expected return on your portfolio?

(More specifically I know that the Beta of risk-free is zero, but I don't know what the beta is of the market index. How do I find that?) I guess just please include all of the steps.

Given Final answer provided was 13.43 for reference