Welcome to your interview.
The question is on your right: Investigate ROAS Drop. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
If a paid media channel suddenly shows a drop in return on ad spend, how would you investigate the root cause for American Airlines?