The following table gives the sample ACF and sample PACF for a time series with 100 observations. k12345678 rk 0.35 0.17 0.09 0.06 0.01 0.01 0.04 0.07 kk 0.35 0.34 0.25 0.18 0.11 0.13 0.14 0.05 Based on the above information, suggest two ARMA models for the data. Explain your answer. i. Given the AR(2) process Xt = 0.3Xt1 + 0.04Xt2 + at, where at is white noise. Is the process stationary? Calculate 1. ii. Using the linear difference equation approach, find the general expression for k, k 2