So how do we figure out this sum? Well now I'm going to do a little bit of mathematical trickery or gymnastics, but it's all valid. And if any of y'all have seen the proof of taking a infinite geometric series, then we're going to do a very similar technique. What I'm going to do here is I'm going to think about well what is one minus P times this expected value? So let's do that. So if I say one minus P times the expected value of X, what is that going to be equal to? Well I would multiply every one of these terms by one minus P. So one P times one minus P would be one P times one minus P. You would get that right over there.