And so we have whatever here that we were integrating, but it's now going to be a function of t. And so in order for this to be equal to zero, we need to figure out when does r of t minus d of t equal zero. And lucky for us, we've already typed in r of t minus d of t. We've defined that as y sub one on our calculator. So let's go back here. And now I can use the solver. So go to math, and then let's see if I scroll up. Let's see, I get to the solver. I could have scrolled down as well.