This question will be marked out of 8 marks and this mark will be converted to a mark out of 2 for the purpose of establishing a final mark for your assignment 3. Let Y be a stationary. series and consider the following AR(1) model Y2 0.8Y-1 + et where et i.i.d. (0, 1). Derive, step-by-step, the mean of Y (4 marks) and the variance of Y (4 marks).