Please help with part d and c

A stock has a beta of 1.25 and an expected return of 12.3 percent. A risk-free asset currently earns 4.05 percent. What is the expected return on a portfolio that is equally invested in the two assets? If a portfolio of the two assets has a beta of 0.85, what are the portfolio weights? If a portfolio of the two assets has an expected return of 11.5 percent, what is its beta? If a portfolio of the two assets has a beta of 2.45. what are the portfolio weights