Question: Chisholm Trail Casino is a casino that opened in Duncan, Oklahoma in October of which year, the casino is 70 miles south of Norman, a city in the U.S. state of Oklahoma 20 mi south of downtown Oklahoma City?
Sentence (from "Norman, Oklahoma"): Norman's estimated population of 120,284 in 2015 makes it the third-largest city in Oklahoma, and the city serves as the county seat of Cleveland County.
Relevant evidence: No