Ms. Sandra L. Helton is Independent Director of Principal Financial Group Inc. Ms. Helton was Executive Vice President and Chief Financial Officer — Telephone and Data Systems, Inc. ("TDS"), a diversified telecommunications organization that includes United States Cellular Corporation, from 1998 through 2006. As of December 31, 2006, TDS served 7 million customers/units in 36 states with annual revenues of $4.5 billion. In her role, Ms. Helton had responsibility for the Finance, Information Technology, Strategic Planning, Corporate Communications, and Corporate Secretary functions. Prior to joining TDS, Ms. Helton spent 26 years with Corning Incorporated, where she held engineering, strategy and finance positions, including Senior Vice President and Treasurer from 1991 — 1997. She also served as Vice President and Corporate Controller of Compaq Computer Corporation from 1997-1998. Ms. Helton graduated from the University of Kentucky in 1971 with a B.S. degree in mathematics, summa cum laude, and earned an S.M. degree from Massachusetts Institute of Technology's Sloan School in 1977 with double majors in Finance and Planning & Control.