NEW YORK CITY — GFI Realty Services has arranged the $8.3 million sale of 4112 4th Ave., a mixed-use building in Brooklyn. The 43,280-square-foot building contains 57 apartments and seven stores. The building is centrally located to the Gowanus Expressway as well as the D, N and R subway lines. Erik Yankelovich of GFI Realty Services represented the buyer, a local family, in the transaction. Joseph Landau of GFI represented the sellers, a partnership of local investors.