You observe the stock returns on two publicly-traded commercial banks, Swell Gofar (SG) and P.J. Gorman (PJG). Their historical returns for the past three years are: SG: 30%,45%,15% PJG: 20%,30%,5%. Consider a portfolio that consists of 40% of SG and 60% of PJG. Calculate the standard deviation of this portfolio. a. 20% d. 23% b. 21% e. 24% c. 22%