Answer: $1.04 per box
Step-by-step explanation
The total sales of A20 box = 430,000 boxes
Variable cost per unit = $0.80
if it outsources the production, then it can reduce fixed costs by $103,200
currently the costs of producing the 430,000 boxes = (430,000 x $0.80) + $103,200 = $344,000 + $103,200 = $447,200
so it should be able to pay up to $447,200 / 430,000 boxes = $1.04 per box, although it would be best to pay less.