The following table shows various sports played by students in a school.
`{:("Sport","Football","Volleyball","Badminbton","Chess"),("Number of students",68,34,56,42):}`
If we respresent these value in the form of a bar graph, then the height of the bar corresponding to football is 13.6 cm. Find the difference between the height of the bars corresponding to volley ball and badminton.
A. 4.4 cm
B. 6.8 cm
C. 8.8 cm
D. 7.7 cm