Consider the following four portfolios: (i) 50% in Treasury bills (with a non-risky rate of return), 50% in shares of stock W (ii) 50% in shares of stock W, 50% in shares of stock X, where the returns are perfectly positively correlated (i.e the coecent of correlation is equal to 1) (iii) 50% in shares of stock X, 50% in shares of stock Y, where the returns are uncorrelated (i.e the coecent of correlation is equal to 0). (iv) 50% in shares of stock Y, 50% in shares of stock Z, where the returns are perfectly negatively correlated (i.e the coecent of correlation is equal to -1). In which of these cases would the standard deviation of the portfolio be exactly midway between that of the two securities? Explain.