Task: Question Answering
Input (English): Passage: In the spring of 1948 Pei was recruited by New York real estate magnate William Zeckendorf to join a staff of architects for his firm of Webb and Knapp to design buildings around the country. Pei found Zeckendorf's personality the opposite of his own; his new boss was known for his loud speech and gruff demeanor. Nevertheless, they became good friends and Pei found the experience personally enriching. Zeckendorf was well connected politically, and Pei enjoyed learning about the social world of New York's city planners.His first project for Webb and Knapp was an apartment building with funding from the Housing Act of 1949. Pei's design was based on a circular tower with concentric rings. The areas closest to the supporting pillar handled utilities and circulation; the apartments themselves were located toward the outer edge. Zeckendorf loved the design and even showed it off to Le Corbusier when they met. The cost of such an unusual design was too high, however, and the building never moved beyond the model stage.
Pei finally saw his architecture come to life in 1949, when he designed a two-story corporate building for Gulf Oil in Atlanta, Georgia. The building was demolished in February 2013 although the front facade will be retained as part of an apartment development. His use of marble for the exterior curtain wall brought praise from the journal Architectural Forum. Pei's designs echoed the work of Mies van der Rohe in the beginning of his career as also shown in his own weekend-house in Katonah in 1952. Soon Pei was so inundated with projects that he asked Zeckendorf for assistants, which he chose from his associates at the GSD, including Henry N. Cobb and Ulrich Franzen. They set to work on a variety of proposals, including the Roosevelt Field Shopping Mall. The team also redesigned the Webb and Knapp office building, transforming Zeckendorf's office into a circular space with teak walls and a glass clerestory. They also installed a control panel into the desk that allowed their boss to control the lighting in his office. The project took one year and exceeded its budget, but Zeckendorf was delighted with the results. 
Question: What office building did the team that designed the corporate building for Gulf Oil redesgn after adding more associates?
Output (English): Webb and Knapp.