Consider the ARIMA(0,0,0) x (0,0,1)2 given by Yt =Vt + aVt - 2 , where |a|t is the WN(0,s2 )
i. Is this process invertible? Why? if it is, find the coefficients in the expansion Vt = ? cj Yt - j , j from 0 to 8.
ii. Find the m-step ahead forecast of Yn+m ( and its variance) based on the infinite past.