An investor wants to create a portfolio between 3 different types of stocks that will balance the expected return of the investment with its risk (measured by the variance of the portfolio). Historical returns (as % of the investment) for the last 4 years for each of the three stocks are shown in the following table:

	Year 1	Year 2	Year 3	Year 4
Stock A	15.3	12.4	11.8	13.6
Stock B	8.4	8.2	9.3	10.1
Stock C	10.3	8.4	11.7	12.1

1. Using Markowitz's mean-variance model, write out the non-linear programming model that would minimize the total risk (variance) while achieving a minimum return of 11%.
2. Using Excel's Solver (with the GRG non-linear solution algorithm), what is the optimal solution (i.e., what percentage of the investment should be put into each of the three stocks)?