At age 83, Robert Caro pulls back the curtains on his process, in his new book "Working." He also answers the question he is asked most often: why does it take him so long to write his books? Caro is the author of the Robert Moses biography "The Power Broker" and "The Years of Lyndon Johnson," The biographer, who has spent much time doing what he does best in the Allen Room of The New York Public Library, returns to share some stories of his own with William P. Kelly, The New York Public Library's Andrew W. Mellon Director of the Research Libraries.