You have three assets X, Y and Z with expected returns of 10%, 15% and 20%, respectively. The weights of the first two assets are 50% and 70% respectively. The standard deviations of the returns for assets X and Y are 3% and 5%. The covariance of assets X with asset Y is 20%, the covariance of asset Z with asset X is -30%, the covariance of asset Z with Y is 10%, and the covariance of asset Z with Z is 36%.
Calculate the expected return and the variance of your portfolio.