2. (a) Given an initial condition for yo, answer the following questions, where y, is the random variable at time 1, & is the error, t is also the time trend in (iii): (i) find the solution for y, where y =y-1+&+0.3-1. (ii) find the solution for y, and the s-step-ahead forecast E[yr+s] for y = and explain how to make this model stationary. 1.2y-1+& (iii) find the solution for y,, and the s-step-ahead forecast Ely+s] for y=y-1+1+& and explain how to make this model stationary