Quarterly demand for smartphones at a retailer is as shown. After obtaining initial estimates for level, trend, and seasonal factors, forecast quarterly demand for year 5 using Winter’s model with α =

0.05, β = 0.10, and γ = 0.15. Evaluate the MAD, MAPE, MSE, bias, and TS for the forecast. Can you find values of α, β, γ that result in a lower MAD or MSE?