Atlantic City (AP) - Trump Plaza Hotel and Casino will eliminate smoking on its casino floor, bringing to six the number of Atlantic City casinos that will ban smoking while gambling. No timetable was announced, but other casinos said they expected to the changes to take effect at their own facilities by next spring. All 11 casinos here must tell the state by Saturday how they intend to comply with a partial smoking ban enacted by the Atlantic City Council in February mandating that at least 75 percent of the casino floor be smoke-free.