suppose that the daily log return of a security follows the following autoregressive model:

Rt=0.05+7/6 Rt-1 + 1/6 Rt-2 - 1/3 Rt-3 + at

where at is a Gaussian white noise series with mean zeros and variance 0.2

1. verity that the mean series{Rt} is a weakly stationary process. If it is not weakly stationary, find an equivalent model that is weakly stationary. Denote the weakly stationary process as Yt (this may be equivalent to Rt)

2. what are the mean and variance of the time series Yt?

3. compute the lag-1,lag-2,and lag-3 autocorrelation of Yt.