Table 21: Actual sales data for the reading glasses during 2021 QUESTION 4 (20 marks) Using the sales data of the reading glasses in Table 21 (question 3), answer the following quostions: 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 respecively and 0.3 for the middle month (show all workings). (9 marks) 4.2 Determine the Mean Absolute Deviation (MAD) of the three-month-weightad-movingaverage monthly forecasts for the April - December 2021 period. (4 marks) a. The linear regression equation of the sales of reading glasses for the 2021 financial year is given by the expression: y=201.4x+4091 (where ' y ' denotes monthly sales, and ' x ', the number representing the month. For example, x=1,2,3, elc., if the month is January, February, March, etc.). Use the regression equation io determine the Mean Absolute Deviafion (MAD) of the regression forecasts for the April - December 2021 period. (5. marks) b. Which of the two methods is better at forecasting the sales of the reading classes? Explain. (2 marks) Table 21: Actual sales data for the reading glasses during 2021 QUESTION 4 (20 marks) Using the sales data of the reading glasses in Table 21 (question 3), answer the following quostions: 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 respecively and 0.3 for the middle month (show all workings). (9 marks) 4.2 Determine the Mean Absolute Deviation (MAD) of the three-month-weightad-movingaverage monthly forecasts for the April - December 2021 period. (4 marks) a. The linear regression equation of the sales of reading glasses for the 2021 financial year is given by the expression: y=201.4x+4091 (where ' y ' denotes monthly sales, and ' x ', the number representing the month. For example, x=1,2,3, elc., if the month is January, February, March, etc.). Use the regression equation io determine the Mean Absolute Deviafion (MAD) of the regression forecasts for the April - December 2021 period. (5. marks) b. Which of the two methods is better at forecasting the sales of the reading classes? Explain. (2 marks)