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

Develop a forecast for the fourth quarter using a three-quarter, weighted moving average. Weight the most recent quarter .5, the second most recent .25 and the third .25. Do the problem using quarters as opposed to forecasting seperate months.

	Last Year	This Year
January	300	275
February	400	375
March	425	350
April	450	425
May	400	400
June	460	350
July	400	350
August	300	275
September	375	350
October	500
November	550
December	500