1. a) The necessity of imposing such controls in order to attain and maintain a national ambient air quality standard;
2. b) The social, environmental, and economic impact of such controls; and
3. c) Alternative means of providing for attainment and maintenance of such standard.

"Reasonably Achievable Control Technology" or "RACT" means devices, systems, process modifications, or other apparatus or techniques that are reasonably available taking into account: