I will admit I was a little confused over the fact you said A1 intercepted the ball.
Team A was on offense at the start of the down in rulebook language. I will give you a pass if you are not a football official (I am not sure you are at the time of posting this).
If you call a penalty for Unsporting or Personal Foul, it can be tacked onto the scoring play.
You give the scoring team the option to take the penalties on the try or the kick off.
Peace