Question: The London, Kentucky micropolitan area is made up of how many counties, in the Eastern Kentucky Coalfield, the part of the Central Appalachian bituminous coalfield, including all or parts of 30 Kentucky counties?
Sentence (from "Eastern Kentucky Coalfield"): The region is known for its coal mining; most family farms in the region have disappeared since the introduction of surface mining in the 1940s and 1950s.
Relevant evidence: No