How to add the Total line on the line graph

I want to add total line on the below image. Below image is a trend graph of sales amount based on category, can I add a total line which sums up the sales amount of all the category over time ?

2 options here.
a. I would use a clustered bar combo chart or a Stacked Bar combo chart which includes by default the line with the totals.
b. If you want to use a line chart, you can create 2 line charts and overwrite them using “free-form” layout. See the attached screenshot. It contains a base Line chart like the one you have and a second Line Chart where the Value contain the total Sales. You have to adjust the Y and X axis and the steps to be the same in both charts to make the visual look like a single one.