Unable to create chart because of merged cells

[sabha]

Hello
I need some help in generating a chart. Please see the attached file. I want to chart the total marks on primary axis (bar) and percentage in secondary axis (line). For some reason it is not coming up properly due to merged cells. Please help.

Also suggest a chart where lot of parameters can be plotted from the table in one single chart and yet making it presentable without any confusion.