Answer:
Some information was missing, so i looked it up:
State of        Prob. of the state      Sunglasses       Umbrella
the economy    of the economy       Company        Corporation
Sunny              .50                25%              0%
Rainy              .50                0%              25%
expected returns:
Sunglasses Company = 0.5 x 25% = 12.5%
Umbrella Corporation = 0.5 x 25% = 12.5%,
so the expected return of the portfolio = (12.5% x 0.50) + (12.5% x 0.50) = 12.5%
standard deviation:
Sunglasses Company = √{[(0% - 12.5%)² + (25% - 12.5%)²] / 2} = √156.25 = 12.5%
Umbrella Corporation = √{[(0% - 12.5%)² + (25% - 12.5%)²] / 2} = √156.25 = 12.5%
so the standard deviation of the portfolio = 12.5%
