A simple forecasting method for weekly sales of flash drives used by a local computer dealer is to form the average of the two most recent sales figures.

Suppose sales for the drives for the past 12 weeks were Week: 1 2 3 4 5 6 7 8 9 10 11 12 Sales: 86 75 72 83 132 65 110 90 67 92 98 73

a. Determine the one-step-ahead forecasts made for periods 3 through 12 using this method.

b. Determine the forecast errors for these periods.

c. Compute the MAD, the MSE, and the MAPE based on the forecast errors computed in part (b).