In the biggest office real estate transaction in the East Bay and the second largest lease in the San Francisco office market thus far in 2002, Safeway Inc., a Fortune 50 company and one of the largest food and drug retailers in North America, has expanded its headquarters. The Pleasanton-based company signed a three-part, 5-year deal for 143,341 square feet to serve as a central location for the company's purchasing department in the CarrAmerica Corporate Center at 4440 Rosewood Dr. in Pleasanton, CA.