(b) Suppose that from a stationary time series of length 121, the sample partial autocorrelations are (3511 _ 0. 8. (623 _ 0. 6 (I333 _ 0. 08. and 4544 _ 0.0. Based on this information alone which ARIMA model would be tentatively chosen for the series? (3 marks) ( ) For a time series of 169 observations, we nd that 31 0.41. 32 0.3 I3 0. 26. 34 0. 21, and 35 _ 0.16. Which ARIMA model ts this pattern of autocorrelations? (4 marks) (d) If { I} satisfies an ARM ) model with (I3 301' about 0. 7, how long should the series be if we need to estimate|(I-3 _ p1 with 95% condence that our estimation error is no more than :01?r