Line Plots · Hard problem

A line plot shows the scores on a $10$-point quiz. Above $6$ there are $2$ X's, above $7$ there are $3$ X's, above $8$ there are $4$ X's, and above $9$ there is $1$ X. The teacher finds a mistake in the answer key and gives every student $1$ extra point. What is the total of all the students' new scores?