1. Download the smelter cost data and open it in Excel.

2. Calculate the marginal cost for each smelter by adding a new row that sums the appropriate cost items.

3. Sort the smelters according to the measure of marginal costs you created in step 2.

4. Create a measure of total cumulative capacity in each column. This will tell you how much capacity is more efficient than any particular plant.

5. Create a graph of the supply curve by making an "XY" scatter plot of the marginal cost and cumulative capacity measures you created above.