Go through the bar chart given below and solve the questions based on it.
The bar chart shows average marks obtained in four different subjects for different years at A R Academy. Marks obtained in any subject in any year can be the multiples of five only.
The percentage increase in the average marks in Maths in 2006 with respect to the previous year = N% and the percentage increase in the average marks in Chemistry in 2006 over the previous year = M%. Find M – N.