4. The following data gives the number of battery sales by one of the leading automobile company over the period of last six months. Month Actual Battery Sales January 39 February 44 March 40 April 45 May 38 June 43 a. Forecast the sales for the month of July using a 3-week moving average method. b. Forecast the sales for the month of July using a 3-week weighted moving average, with weights of 0.5, 0.3 and 0.2. Using 0.5 for the most recent month. c. Compute the forecast for the month of July using exponential smoothing with a -0.5.(Assume the forecast for January was 39 batteries) d. Compute the errors of the of the forecast based on calculation in c