Plaintiffs-appellants are former employees of the Dun & Bradstreet Corporation ("Dun & Bradstreet") who were terminated from the company when Dun & Bradstreet sold its "Receivables Management Services" operations, conducted in the United States, Canada, and Hong Kong, on April 30, 2001. Upon the sale, plaintiffs-appellants became employees of a new corporation, "Dun & Bradstreet Receivables Management Services," which resulted from the sale. Their change in employment did not qualify them to receive severance benefits under the "Career Transition Plan," a Dun & Bradstreet benefit plan. It also affected the retirement benefits that they could receive under another benefit plan, the "Master Retirement Plan," which on December 31, 2001 was replaced by the "Dun & Bradstreet Corporation Retirement Account Plan." The new pension plan established as the Dun & Bradstreet Corporation Retirement Account Plan created different retirement benefits but assumed the vested obligations of the superseded Master Retirement Plan, which is at issue in this appeal.