Please write the formulas in Excel and show the steps

4) A small manufacturing firm has recorded a time series of the cost per unit for the firm's leading product over the past eight years. a) If you are not given a base value or trend, what would be the forecast for the year 10 made at the end of year 8(=0.2,=0.4). b) Forecast for the year 9 using 1) 5 -month weighted average using 0.1,0.1,0.1,0.2,0.3, with the heaviest weight applied to the recent month 2) Exponential smoothing using =0.2 and forecast of 21 for year 5 3) If value was not provided in the question above, what value of a would you choose