15. The rates of return per dollar invested in two common stocks over a given investment period can be viewed as the outcome of a bivariate normal distribution N(IL, E). The rates are independent between invest·

ment periods. An investment firm intends to use a ran·

dam sample from the N(IL, E) population distribution of rates of return to generate estimates of the expected rates of return, IL, as well as the variances in the rates of return, given by the diagonal of E.