Calculate portfolio returns and its statistics
Year ending	Stock A	Stock B	Stock C		Portfolio Returns
31-Dec-99	28.67%	-7.31%	17.57%
29-Dec-00	61.21%	-11.38%	-20.83%
31-Dec-01	-40.42%	18.80%	43.00%
31-Dec-02	-13.40%	17.28%	-35.45%
31-Dec-03	30.43%	14.56%	20.49%
31-Dec-04	24.89%	20.15%	7.19%
30-Dec-05	37.89%	-0.93%	-15.83%
29-Dec-06	28.40%	18.60%	19.77%
31-Dec-07	-0.11%	7.15%	12.84%
31-Dec-08	-50.07%	-14.14%	-20.79%
Portfolio proportions	0.20	0.50	0.30
				Portfolio average return
				Portfolio variance
				Portfolio standard deviation