a. Make a forecast for July using the exponential smoothing method with the smoothing constant a=0.7. For initial forecast, use the Naive method.

b. Calculate the MAPE (Mean Absolute Percentage Error) of the exponential smoothing method in part (a).

3. The sales of a product over the past six months are shown in the table below. Month Sales January 150 February 120 March 140 April 160 May 170 June 160