3. The following are the sales (in RM) of a company over the last 7 days. Date Sales 1 Oct 754 2 Oct 678 3 Oct 687 4 Oct 765 5 Oct 781 6 Oct 725 7 Oct 801 8 Oct ? 9 Oct a) By using 3-days weighted moving average as given [9 marks] Ym = 0.5 Ym-1 + 0.3 Ym-2 + 0.2 Yn-3 predict the sales on 8 Oct and 9 Oct. An additional column of numbers must be constructed. b) By using exponential smoothing with a = 0.6. [9 marks] Y , HI = Y, + a ( Y, - Y,) where 0 So s1 predict the sales on 8 Oct. An additional column of numbers must be constructed. c) Can the sales on 9 Oct be predicted using exponential smoothing? Give grief reasons to your answer [2 marks]