Blocks B and C were each divided into 176 Economic Areas (EA), sometimes referred to as BEA by the FCC. Blocks D, E, and F were each broken up into 12 Regional Economic Area Groupings (REAG), sometimes referred to as REA by the FCC.
The text describes how blocks B, C, D, E, and F were divided into smaller units for economic analysis. The specific names used are "Economic Areas" (EA) and "Regional Economic Area Groupings" (REAG).