(b) If we suspect that the variance of e changes systematically through time what w ould be the consequences for standard OLS estimation. Outline the \( A R C H \) and GARCH models, which would allow us to deal with this problem fully. (c) If you believed that the variance of e affects the return on the bond how would adapt the GARCH model to allow for this. (d) If you were investigating a model such as the capital asset pricing mocel which used the covariance between the market return \( r_{m} \) and the bond return \( r \), how could the GARCH model be extended to allow for this case?