The question is, in an m/m/k queue, what is the expected number of jobs?

So, I'm looking for E(i) (we have i denoted as the number of jobs in the entire system). I'm not quite sure how to go about doing this. The only idea I had was that you could sum all of the entries in the stationary distribution and multiply them by the number of jobs they represent...but this seems too easy. Can anyone please point me in the right direction?
Thanks!