Jordan Moreau Harbor Group International, a privately owned real estate investment and management firm, announced Monday it has entered an agreement with ViacomCBS to purchase the CBS Building in New York City for $760 million.Commonly referred to as Black Rock for its gray granite architecture and dark tinted windows, the 38-story office tower is located at 51 West 52nd Street in midtown Manhattan.ViacomCBS will lease back its space on a short-term basis, and HGI plans to implement a