This report is based on results of the TERC Modeling Project funded by the National Science Foundation grant MDR-8550373. Any options, findings, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the Foundation.We gratefully acknowledge the support of Apple Computer, Inc.Apple, Macintosh are trademarks of Apple Computer, Inc.Stella is a trademark of High Performance Systems, Inc.Excel is a trademark of Microsoft, Inc.