 Hi, this is Dr. Don. I have some hints and help, I hope, for M8A1 problem number one. Now, I built this template trying to help people come up with a structure for the decision model that was fairly straightforward given the fact that when I taught this in an earlier term students really got confused and had crazy looking decision models. But I'm thinking maybe I oversimplified it so much that it's more complex. What we have here is a situation which FAS has to buy copper for its four plants over here from these five different companies. And we need to minimize the total cost of the copper. This row here has the cost of the copper that we buy from each of the five plants. And this row has the cost of the shipping from the copper that we buy from each of those plants. And you sum those up and then add the cost of copper and the cost of shipping to get the total cost, which is what we're going to minimize with solver. These are our decision variables in this matrix here. I'm going to highlight those and just make those red for the moment. So emphasize the fact that those are the decision variables. And then the other things I have here are just templates, places for you to put the information you need to build your decision model. Let's start here. We've got the copper prices per ton. And I'm going to go over here and I can see I've got them in that row right there. So I'm going to select that row, control C, control Charlie, and just paste it in right there. So now we've got that information. The next thing we need over here is this matrix that the cost of shipping differs from company to company and from company to plant. So we have a four row by five column matrix. And I've given you the information over here. It costs $9 per ton for company one to send copper to plant one. So I'm just going to highlight that matrix, control C, and I want to paste it in over here, control V. So now we've got that information. The next thing we need dropping down in this decision model is the plant demand. Now I messed up a little bit trying to make it fit that title. These are merge cells, so I'm going to go there and click on unmerge to put them in a simple cell, and then I'm going to highlight those, control C, and paste those in that demand area. So those are the demands that we've got to meet. Those are the constraints. We've got to supply at least that much for each of these plants. Now we need a similar thing, the available supply. Each company can only supply a certain amount, and we've got that in this row up here, the available supply in tons, control C, and I'm going to paste that in down here. Now we've got most of everything we need to build the decision model, and if you think about it, what we're doing here, we're going to use the table down here to sum up and get the cost of the copper from each of the five companies, and then the shipping total from each of the five companies. Add those two things together to get the total cost, and then optimize that. Let's give you an example. Here we go to company one, shipping to plant one. Let's just say we want to buy 10 tons, and again, you don't have to set this to an integer if you don't want to. You can leave it as decimals or you can set them to integers. Let's just say for plant two, they want 15 tons, and we can go down into this cell and say, okay, how much have we bought from that company? We can just sum that up equal. I'm not going to use the sum function, but you would. That plus this gives me the total purchase from each company, and when you get through you would compare this cell to the constraint there because you can't buy more than they have available. Then we would go over here. Total bought from each plant, and again you would sum up equal this plus that. So far we've only bought 10 tons and need 430, so we've got a long way to go. Now let's get some cost down here. The cost of copper, click in that cell, equal, and it is the cost per ton from company one times the total purchased from that company. So far that's just 25 times, $50 is $1,250, and you can see I've already got the sums over here, all that's already adding up. The cost of shipping from company one so far, we hit equal, and it would be the cost from company one to plant one times the amount bought from company one for plant one, plus the cost from company one to plant two times the amount bought for plant two, and I'm just going to stop there. You'd have to continue, and that gives me the total cost of shipping so far, and of course you would have to complete the matrix in order to come up with the total cost of the copper you buy and the total cost of shipping. Now I just showed simple addition, you can use sums, you can use products, you can use some products, whatever you're most comfortable with to come up with this row here. And of course when you do the solver you've got to check each of these rows here against the demand, you've got to supply at least that much, and here you cannot purchase more than is available, so those are the constraints. So I hope this helps you get going.