Which of the following is true about calculating expected portfolio returns and variances? Select one: O a. Portfolio return can be calculated using the expected return and portfolio weight for each asset. ob. You need to calculate the weight of each asset relative to the total portfolio to calculate the portfolio return, but not to calculate the portfolio variance. O c. The portfolio return is not needed to calculate the portfolio variance. d. The portfolio return and variance are independent of the possible states of nature. e. The portfolio variance is generally a weighted average of the variances of the individual assets