【General guidance】The answer provided below has been developed in a clear step by step manner.Step1/6a)To forecast January sales by using naïve method, 3 month moving average, six month weighted average, exponential smoothing and trend projection methods1.Forecast as per naïve methodNaïve method assumes demand in the next period is equal to the demand in the recent period.Now substitute January month demand 20 with December's demand i.e. 23. As mentioned above whatever the demand in December is equal to the demand in January so 23 is consideredHence according to naïve method the forecast for January is 23.Explanation:Please refer to solution in this step.Step2/62. To forecast as per three month moving average methodMoving approach= Σ Demand in Previous n Periods / nNow substitute 20,21,23in demand in previous month's n periods and 3 in nF = (Month 1 + Month 2 + Month 3) / 3 = (20+21+23)/3 = 21.33Hence as per the moving average method the forecast is 21.33Explanation:Please refer to solution in this step.Step3/63.To forecast as per sixth month weighted average methodWeighted Moving Average =(Σ(weight for period n) (demand in period n))/Σ WeightsThe given weights is 0.1, 0.1, 0.1, 0.2, 0.2, & 0.3 using three month approach now multiply weights with last Sixth Month substitute 17, 18, 20, 20,21,23Moving Average = 17×0.1+18×0.1+20×0.1+20×0.2+21×0.2+23x0.3 = 20.6Hence as per weighted average method the forecast is 20.6Explanat ... See the full answer