Consider the stochastic version of the arbitrage pricing model, where Ri (the return of the i th asset) is related to the factors F1 and F2 as follows: Ri=ai+bi1F1+bi2F2+i where i is a random "noise" term with zero mean and variance i2>0. (a) For three assets (1,2 and 3), derive the weights x1,x2 and x3 so that the portfolio has a return x1R1+x2R2+x3R3 that does not depend on the two factors. You can assume that the b 's are such that the relevant arithmetic operations will not result in the "division by zero" problem. (b) Explain whether the portfolio you find in part (a): i. is risk free; ii. should earn the risk-free return rate