The table below shows the quantity of yams in kilogram produced by four yam producing states in country X between 2003 and 2006. 
 

state	2003	2004	2005	2006
A	200,000	300,000	400,000	500,000
B	400,000	400,000	500,000	600,000
C	500,000	600,000	700,000	700,000
D	600,000	500,000	400,000	300,000

(a) Draw a comparative I group bar graph to represent the statistics.

(b) State two advantages of using comparative I group bar graphs in showing statistics.

(c) Name one other method that can be used in showing the statistics.