Please explain in detail and help me understand better. Thank you!

Question 1) What is meant by diversification and how does it relate to common versus independent risk? What is the difference between systematic and unsystematic risk?

Question 2) What information do you need to compute the expected return of a portfolio? Why isn't the total risk of a portfolio simply equal to the weighted average of the risks of the securities in the portfolio?

Question 3) What does WACC measure? Under what assumptions can the WACC be used to value a project?