A time series defined as ???????? = 1000 log10(????????), where ???????? is the price of hogs recorded annually by the U.S. Census of Agriculture over the period 1867--1948, was considered in Exercise 6.6.

(a) Estimate the parameters of the model identified for this series. Perform diagnostic check to determine the adequacy of the fitted model.

(b) Are additive or innovational outliers present in this series?

(c) If outliers are found, perform the appropriate adjustments to the basic ARIMA model and evaluate the results.