5-27 Sales of industrial vacuum cleaners at R. Lowenthal Supply Co. over the past 13 months are as follows:

Sales ($1,000s) Month Sales ($1,000s) Month 11 January 14 August 14 February 17 September 16 March 12 October 10 April 14 November 15 May 16 December 17 June 11 January 11 July

(a) Using a moving average with three periods, determine the demand for vacuum cleaners for next February.

(b) Using a weighted moving average with three periods, determine the demand for vacuum cleaners for February. Use 3, 2, and 1 for the weights of the most recent, second most recent, and third most recent periods, respectively. For example, if you were forecasting the demand for February, November would have a weight of 1, December would have a weight of 2, and January would have a weight of 3.

(c) Evaluate the accuracy of each of these methods.

(d) What other factors might R. Lowenthal consider in forecasting sales?