 Hi folks, it's Dr. Don. I'm going to start with a quick apology. I tried to help some one term before last showing her how to use named cells to help her understand her model and I forgot that I left that in the worksheet that you now have. So when you built your model and you followed the instructions from the last video, you've pasted it into the goal-seek cell. If you try to do the goal-seek problem where you're trying to get this different cell to 100,000 by changing these cells up here, nothing happens. And if you click there, I'm going to click in that cell. I'm going to put in 10, hit enter. The difference delta did not change. The reason for that is that I use those named cells. I click in this total manufacturing cost and you look at the formula that's in that cell. It's fixed cost plus unit variable cost time-demand volume. Now my fixed cost is up here in B6, but you don't see B6 in this formula. You see fixed cost. Unit variable cost is B7, but you don't see B7 times B14th demand. You see these names. Now where are those names coming from? I'm going to go back here to the first tab where you built your model and here if I change this to zero for an update, you can see that my difference delta and everything downstream updates properly. I'm going to click in that cell for fixed cost and you can see instead of B6 it says fixed cost. That's the names. I named these cells. They can be very helpful when you're trying to analyze your model, but it's not helpful when you're trying to copy a model from one worksheet to another because the model is referring to that name cell, which is B6 on this tab, not B6 on this tab. You've got to be aware that one way you should do this thing, probably the cleanest way, is to get rid of all these name cells and you should go up here to formulas, look for name manager. There you can see the five names. I'm going to hold my shift key down and select all five of those, then just click delete. It says, are you sure? Yeah, I want to get rid of them. I've gotten rid of those and now, of course, it shows me all of the cells that are tied back to those names. It's looking for those names. I'm going to go ahead and put 50,000 in there again so we have a value. The easiest way is just to get the practice rebuild your formula equal fixed cost plus unit variable cost times demand hit enter. Now I've got the total manufacturing cost equal the outsourcing unit cost times demand hit enter. Now everything works here properly and if I go back and I can copy this model, control C, go back here to goal seek and just paste over what I've got there. Now it works. If I change this to 10 again, you can see the the models work again. I apologize. The name ranges are really helpful when you get into more complex decision models, particularly when you're doing Solver and Monte Carlo, using name ranges on a worksheet and not copying that model to another worksheet works really well. But since the equations are remembering this specific cell that has the name, you don't want to use it just willy-nilly like I mistakenly got you to do. So I hope this helps.