In 1965, Beckwith and Singer devised a method for production of specialized transducing phages carrying the lac region. In a two-step approach, they first transposed the lac genes to a new region of the bacterial chromosome and then isolated the specialized transducing particles. Prior to these manipulations, they noted that the integration site for the temperate phage f80, designated att80 was located near one of the genes conferring resistance to phage T1, termed tonB (Note: tonB- is the resistance allele). Beckwith and Singer used an F’-lac episome that could not replicate at high temperatures in a cell carrying a deletion of the lac genes. By forcing the cell to remain lac+ at high temperatures, they could select strains in which the episome had integrated into the chromosome (the episome is maintained because it now replicates with the chromosome). By combining this selection with a simultaneous selection for resistance to T1 infection, they found that the only survivors were cells in which the F’-lac episome had integrated into the tonB locus. Why? They placed the lac region near the f80 integration site. Describe the subsequent steps that the researchers must have followed to isolate specialized transducing particles of phage f80 that carried the lac region.