Eight year old Billy learns his parents have decided to get…

Eight year old Billy learns his parents have decided to get a divorce. They will have joint custody, and Billy and his 5- year old sister will spend time at both parents’ house during the week. For the last seven months, Billy has been angry and had temper tantrums more than he used to. He has a low frustration tolerance, has difficulty following rules, has become argumentative with authority figures (both parents & other authority figures) and does not accept responsibility for his behavior. Billy’s diagnosis is?