And then they give us her steps, and at the end they say, is Erin's work correct? If not, what's her mistake? So pause this video and see if you can figure it out yourself, is Erin correct? Or did she make a mistake, and where was that mistake? Alright, now let's just do it together. So she says that this is the derivative. I'm just going to reevaluate it here to the right of her work.