There is some evidence that the Lydia Pinkham data may be nonstationary. For example. the sample autocorrelations tend to be large (persist) for several lags. Difference the data. Construct a time series plot of the differences. Using Minitab or a similar program, fit an ARIMA(1, 1.0) model to annual sales for 1907 to 1948. Generate one-step-ahead forecasts for the years 1949 to 1960. Which model, AR(2) or ARIMA(1, 1, 0), do you think is better for the Lydia Pinkham data?