State the conditions under which the Moving Average method can be recommended for trend analysis. How will you determine the period of the moving average? (a) Calculate the 4-year moving average of the following data related to the sales in a department store. Year 2000 2001 2002 2003 2004 2005 2006 2007 Sales 960 976 974 996 1024 1040 1688 1128 Year 2008 2009 2010 2011 2012 2013 2014 2015 Sales 1144 1120 1140 1168 1196 1212 1200 1180 (b) Plot a time series graph for the above data. (c) Plot the corresponding trend line using the method of moving average.