The PKA value is 8.3. And then for this N group, it's the PKA values 3.1. So we have 123-4567 PK values that we have to consider in steps or in A-B-C and D. So let's begin with A. Okay, so at a PH of two, what is the net charge on this protein? So, let's begin with this group and basically go one by one all the way to the 7th group, this alpha carboxyl group. So at the alpha amino group, we're a PH of two.