Barbara is a 9-year-old female who is brought to counseling by her mother, Julie, because she doesn't know what to do with her daughter. During the intake, Julie indicates that Barbara is always arguing with her and her father. While Barbara is coloring at a nearby table, she interrupts and says, "I don't argue with you and Dad." Julie responds by saying in a loud, frustrated voice, "You were just arguing with me about coming here! You spent 20 minutes refusing to get into the car!" Barbara, continuing to color and not making eye contact with her mother, replies, "That's not arguing. I just didn't get in the car. How is that arguing? I didn't even say anything." Julie rolls her eyes, and returns her attention to you. Julie indicates that Barbara has always been a strong-willed child, but over the past two years, she has become more defiant and angry. During that time, parents from a local play group have stopped bringing their children to play dates when Barbara is there due to her disruptive tantrums and refusal to follow simple directions during games and activities. Barbara's teacher recently sent home a report indicating that she has been arguing with other students during recess. The teacher also reported that someone destroyed another student's art project. She strongly suspects Barbara did it, despite Barbara blaming it on the classroom's pet hamster.

1a. What diagnosis would you give Barbara?

1b. Indicate the specific signs and symptoms Barbara presents that justify your diagnosis and associated specifiers.