public double SumOfSquares(StockPerformance stock1, StockPerformance stock2) { return stock1.Jan * stock2.Jan + stock1.Feb * stock2.Feb + stock1.Mar * stock2.Mar + stock1.Apr * stock2.Apr + stock1.May * stock2.May + stock1.Jun * stock2.Jun + stock1.Jul * stock2.Jul + stock1.Aug * stock2.Aug + stock1.Sep * stock2.Sep + stock1.Oct * stock2.Oct + stock1.Nov * stock2.Nov + stock1.Dec * stock2.Dec; }