Original sentence: Bernard Madoff operated his large Ponzi Scheme which came unraveled in 2008, from the 17th through 19th floors, which was occupied by no more than 24 employees
Edited sentence: Bernard L.Madoff Investment Securities leased the 17th through 19th floors.Madoff operated his $65 billion Ponzi scheme, which came unraveled in 2008, from the 17th floor, which was occupied by no more than 24 employees