Suppose that there are only two stocks in the market and a risk free asset E(Ra)=18% , SD(Ra)=15% E(Rb)=12% , SD(Rb)=7%) COV(Ra,Rb)=0 Rf=5%, Supposed that you want to invest in a portfolio with E(Rp)=15%. a. Calculate the SD(Rp) b. Write down the portfolio's weights for each one of the securities you decided to invest in