Here are the data for the past 21 months for actual sales of a particular product:

2006 2007 January February March April May June July August September October November December 300 400 425 450 400 460 400 300 375 500 550 500 275 375 350 425 400 350 350 275 350 Develop a forecast for the fourth quarter using three different focus forecasting rules. (Note that to correctly use this procedure, the rules are fi rst tested on the third quarter; the bestperforming one is used to forecast the fourth quarter.) Do the problem using quarters, as opposed to forecasting separate months.