Table 2.1: Actual sales data for the reading glasses during 2021

Month	Actual Sales (Pairs of reading glasses)
January 2021	2 800
February 2021	3 000
March 2021	5 000
April 2021	4 000
May 2021	5 600
June 2021	8 000
July 2021	8 000
August 2021	7 900
September 2021	6 000
October 2021	4 050
November 2021	4 900
December 2021	5 550

Using the sales data of the reading glasses in Table 2.1 (question 3), answer the following questions:

4.1 Calculate the three-month-weighted-moving-average monthly forecasts for the period April 2021 - December 2021. Use weights of 0.5, and 0.2 for the most recent and oldest monthly data respectively and 0.3 for the middle month (show all workings). (9 marks)