Mean as a vertical line in a skewed distribution

[DonPepe]

Hi, 

I have a chart like the one below and I want a vertical line representing the mean in this chart. 

Do you know how I can manage to get that ? 

My data are like the one below : 

I have a Key which is a text value and a duration. 

I construct the graphic by counting the number of key for each duration. 

Thanks a lot for your help,

Don