To calculate the variance of a three-stock portfolio, you need to add nine boxes: usea; ror example: x1= proportion invested in stock 1 12= covariance between stocks 1 and 2 For each box, indicate whether the value is correct or incorrect To calculate the variance of a three-stock portfolio, you need to add nine boxes: usea; ror example: x1= proportion invested in stock 1 12= covariance between stocks 1 and 2 For each box, indicate whether the value is correct or incorrect