As Nina and Erin were eating lunch in Central High School student canteen, they were discussing the news coverage regarding the girls' athletic coach being arrested for selling steroids to student athletes. “I think the guy just did it since they do not pay teachers adequate money,” Nina suggested. “I bet the guy had some other type of drug addiction he was willing to pay for,” Erin countered. Nina and Erin's ideas regarding the cause of coach's drug-selling behaviour are illustrations of: