Calculate Dynamic Total Based on Slicer

HI Guys,

I'm trying to sort out numerical data into three categories, like (1-10) can be sorted out into 3 categories as :

Class 1 : 1-3

Class 2: 4-7

Class 3: 8-10

And on the basic on this,( which I choose using a list slicer), I get the individual sum of their corresponding correlated data.

This is done. But what I'm trying to do is now find the grand total of these three sub totals of each category.

Can anyone help me out with this?

Thanks.