When calculating the success/failure of the enemy dive bomber's attack, is there an additive benefit from EACH of the defending ships & aircraft... Or is it just binary, ie. there's at least one defender... Knowing this would make a huge difference to how I set my defences (I'm only asking because I don't see much difference between having one defender versus having lots of them

Also... Does having a defending neighbour unit distract the attacker (ie. reduce the amount of damage it causes) or just cause damage to the attacker?