Among the residential areas with the bad alias "Internal Revenue Service", how many of them are in the Eastern time zone?
"Internal Revenue Service" is the bad_alias; in Eastern time zone refers to time_zone = 'Eastern'
SELECT COUNT(T1.zip_code) FROM zip_data AS T1 INNER JOIN avoid AS T2 ON T1.zip_code = T2.zip_code WHERE T2.bad_alias = 'Internal Revenue Service' AND T1.time_zone = 'Eastern'